As Calob already reflected upon a month ago, the iPhone 3GS has been around since June 2009 and is really starting to stretch the limits of how long we expect a smartphone to be on the market. Not only did Apple make sure iOS 5 would work on it (mostly), they even kept it around as a low budget model that's still being sold. In a day and age where the first-generation iPad from 2010 is even considered something of a relic, Apple actually chose to keep an even older device on the shelves. Who on Earth would use such an old phone these days?
That, ladies and gentlemen, would be me. Yes, I'm still using the 3GS. I bought it on launch day here in Norway on July 31, 2009, and it's been with me through thick and thin ever since. It has seen two major software updates in its lifetime, and it's currently running iOS 5.0.1. So, how viable is the 3GS now, a full two-and-a-half years after its release?
Apple devices don't really follow the same unwritten rules as Android devices, neither for hardware nor software. Android devices are often abandoned by the manufacturers very quickly, but kept around by the hacker community. In other words you can upgrade your older phone, but you certainly won't find it in stores anymore. Hardware-wise there's also a noticeable difference. While the current generation iPad and iPhone both use 1GHz dual-core CPUs and 512MB RAM and are generally praised for their stability and performance, those same specs on the Kindle Fire are being blamed for the lagginess of the device. Android is up to 1.2/1.4GHz dual-core or 1.4GHz quad-core with 1GB RAM now, and even some of those devices see complaints of lag.
The reason I point this out is the hardware of the 3GS. With a 600MHz single core CPU and 256MB RAM, it's a joke compared to pretty much anything high-end these days, at least on paper. I can tell you, though, that this is very much a reality as well. The 600MHz CPU isn't a big deal; most apps aren't really that CPU intensive, the fact that it has 1/4 the resolution of its younger brothers offsets the problem a bit (for both CPU and GPU), and it generally doesn't feel like it's slow in that respect.
The RAM, however, is a whole other issue. Many people think that the iPhone 4/4S and iPad 2 have twice the RAM of the iPhone 3GS and iPad 1. That's only half true. Yes, the former have 512MB and the latter have 256MB. The OS however doesn't use twice as much RAM on the better equipped devices, which means that the amount of free RAM is roughly triple on the 512 devices compared to the 256 devices.
My 3GS, for instance, has roughly 100MB free RAM when it's not doing anything and nothing is running in the background. My iPad 2 on the other hand has about 280MB. In iOS land, 280MB will last you a lifetime. 100MB however…not so much. It's the reason the iPad 2 is such an upgrade to the iPad 1 and it's definitely part of the reason the iPhone 4(S) is such an upgrade to the 3GS. When RAM gets low, the phone turns slow. Feel free to make a t-shirt out of that one.
In practice, this means that you need to have an app that can free RAM on your home screen. I use Memory Doctor, which both lets me see how much free RAM I have and gives me a button to free up memory if it's getting low, which happens a lot. After a few apps have been opened, the amount of free RAM drops to 5-10MB and the UI becomes very laggy. Hit that magic button in Memory Doctor and it clears that up again. It's an annoyance, but it is absolutely necessary, as just closing apps from the multitasking bar won't always do that much.
Then you have the camera. The iPhone 4 was really the first phone Apple made that had a good camera, and the 4S improves on that even further. The 3.2-megapixel camera on the 3GS isn't bad in terms of 2009 standards, but it isn't good either – and it's definitely not a match for 2011 standards. It's good enough to take quick snapshots to show your friends something, but you're not going to be selling your standalone digital camera in favor of it.
The 3GS is also missing a few other hardware features that the new phones have. The gyroscope is one example, though that's mostly for gaming. The front-facing camera is another, and that's for Facetime and things like Skype. I also think there is something new with the GPS in the 4/4S that allows it to be used more frequently without draining the battery, as the 3GS is unable to use the location-based reminders that the newer phones can use. Since these require the phone to detect when you are certain places, it needs to use the GPS (unless they went for cell tower triangulation, which I doubt).
The screen is obviously a big difference, with only a quarter as many pixels as the newer phones. I refuse to ever use Apple's idiotic biology-defying marketing term for those high resolution displays, by the way. In practice, the screen looks older. Videos and images more pixelated, icons and text less sharp, and so on.
It's not really an issue, though, if you ask me. Seeing as this is a touchscreen phone, the size of buttons and other interface elements will be dependent on the size of a finger, not a set number of pixels. While the iPad's physical screen size makes the resolution boost much more useful in that you have a lot more room to fit physical size-dependent buttons, the increased resolution of the iPhone 4 and 4S really only make things look better. That's not a "feature" to be ignored of course, by any means, but it's something to keep in mind if you're used to the advantages you get from having a higher resolution PC screen.
As far as software goes, the 3GS is pretty up to date. It's starting to fall behind on newer games and such, but a lot of the software that exists on these phones is pretty simple. Email, calendar, contacts, news, stocks, weather, and so on is just as easy to get to on the 3GS as on newer phones. This is the kind of apps I personally use on my 3GS.
My most used app is the clock, in terms of seeing what the time is, setting alarms, and setting timers. After that, it would have to be email. I very rarely write any emails, but I do check them. I use text messages more or less exclusively to do banking, while most my chats happen over IM services on my PC or iPad. The phone part isn't even used much, mostly for an incoming call every now and then. Skype all the way, baby!
Other apps I use include postal tracking software, public transport time tables and live updates, and tools like authentication code generators, unit converters, etc. In other words, I use quite a lot of PIM (Personal Information Manager) apps.
Of course the usability of the iPhone 3GS from a software point of view depends on the person who's going to use it. If you want to play games, you won't get it. If you think Siri (the new voice control system on the 4S) will be an indispensable tool then you definitely won't get it. If you're like me and mostly use it as a PDA, however, you will do fine with a 3GS.
In the US, a 2009 iPhone 3GS is now no longer tied to a contract. A 3GS you buy now, however, will be tied to one for two years, which will make the 3GS even more outdated by the time that contract period ends. I d oubt that Apple will make iOS 6 and 7 backwards compatible that far, so that's definitely something to keep in mind.
The US system of carrier contracts is very different from many other countries, though. Here in Norway, 12 months is the longest that any such contract can be – by law. That means that 2009 iPhone 3GSes have been out of contract for one-and-a-half years, and even 2010 3GSes bought around Christmas are about to be out of contract. Carriers also have to list the total cost of ownership of the device whenever they list the "pick up price," so that $0/$99$199 pick up price system in the US means nothing over here. The total cost of ownership/price with $0/month plans (they also can't force a plan on you just because you have a certain device) is roughly 3000/4000/5-6000 NOK, respectively.
The point here is that your choice in picking an iPhone or choosing whether to upgrade depends highly on the carrier system in the country you're in. Personally, I'm keeping the 3GS for a very simple reason; out of contract, I can choose a plan that costs me about $20 per month for everything I do on the thing, data included. With the high prices on things here in Norway, that's more like $10 in the US I'd imagine, as $20 gets you one of the smaller medium burger menus at McDonald's in Norway. I'm not tying myself to a new 12-month contract with a more expensive plan to subsidize the purchase of one of the newer models. Obviously it's very different if the upgrade cost is relatively speaking much lower or if you're buying "from scratch."
The 3GS is still a capable phone for a lot of things, specifically information gathering and management. Compared to current generation dumbphones it's still "high tech" and the fact that it can run iOS 5 and most of the apps in the App Store means that for some uses it's more powerful than week-old top-of-the-line phones that run other OSes.
For other uses, it's completely outdated and useless. Basically, it all comes down to what you'll be using it for. If you have a 3GS from 2009 that's also different than facing the choice of buying one now as the battery might have lost a lot of capacity or be near death. Replacing it costs money, which is important to keep in mind.