The Samsung Galaxy Tab is a good device out of the box. Third-party apps from Android Market and elsewhere make it great, and having root access makes it even better.
Rooting the Tab opens up a world of possibilities that would otherwise be out of reach. Root access gives you complete control of the system, which means you can do much more with the device than Samsung and your carrier probably want you to do. It lets you install awesome root-only apps, uninstall apps that can't normally be removed, do complete backups (Nandroid), flash custom ROMs, apply themes, change boot animations, and more. Note: Some of this isn't possible on the Tab yet, but I have no doubt that it will be soon.
In other words, root access is something that you definitely want on your Tab . . . as long as you're comfortable with voiding your warranty. There are ways to unroot and flash the stock recovery image (if you flashed a custom one) to cover up your tracks in case you ever need to send the device in for repair, but there's no guarantee that you'll get away with it. In other words, rooting is not completely risk-free and anything you do is at your own risk.
There's more than one way to root the Galaxy Tab, but the easiest method is to use a one-click root app called z4root.
One-click root apps aren't new (Universal Androot, for example, has been around for months), but z4root is what I used to root my Tab so it's what I'm recommending.
Here's how to use it to root the Tab:
1. Download z4root from Android Market (direct link) and install it.
2. Enable USB debugging on your Tab by pressing the Menu button then tapping Settings -> Applications -> Development -> USB debugging.
3. Open z4root and press the "Root" button.
4. Don't panic when the Tab restarts. It's supposed to do that.
When it's fully booted, you won't get any kind of confirmation of your success. Everything will look exactly the same. Open z4root again, though, and you'll see this:
Another way to confirm your new root access is to look for the newly installed Superuser app in your app drawer/tray.