The ability to expand the storage in a mobile device is something many people consider a must-have. I still remember the Nokia N800's dual SD card slots, a feature I really wish was in more current-day devices.
The great thing about memory cards is that they actually get cheaper, and much faster than internal storage does. Apple just released the iPad 3 with the same storage options and prices as last year, which puts the 48GB difference between the lowest and highest capacities at an insane $200. Meanwhile, the least few months have seen microSDHC cards fall drastically in price, especially when it comes to the 32GB variants.
A 32GB microSDHC card can now be had for about $20+ in the US, and about £20 (sometimes less) in the UK. That's a price it's hard to argue with, especially considering how expensive these cards used to be. Even compared to just a year ago, the current price is a mere 1/4 of that. The cheapest cards are slow though, which is noted by their class rating. I personally tend to stick to class 10 cards these days, which bumps up the price a little bit, but for anyone who has watched a file transfer to a class 2 card it's hard to call and extra $5-10 "expensive".
What's also notable about the 32GB capacity level is that it marks the end of the SDHC standard. While a lot of 64GB SDXC cards work on current SDHC capable devices if you change the file system from exFAT to FAT32, we're now at the official final stage of upgrades for pretty much all the devices that have come out over the last few years. Exactly when SDXC is going to be a standard in new devices I don't know, but I really hope it's soon. It's not just about being able to use bigger cards, but also about fixing one of the biggest issues with storage on Android today: no support for files above 4GB (on external storage anyways). With microSDXC support and the new exFAT file system, it will finally be possible to store files larger than 4GB on those cards and still have Android recognize them.
Either way, if you own a microSDHC compliant device, you can now make the final upgrade knowing that you'll have to buy a new device before you can upgrade next time (officially, anyways). A 64GB microSDXC card will currently cost you well over $100 most places anyways, so that alone is going to make 32GB cards look more attractive.