I don't like the XperiaPlay, I can't game with those Touch(exAnalog)Sticks. Instead of sticks, there are touch surfaces. Don't like it
I know, they could at least have made them like on the Nintendo 3DS, but e.g. for Gameboy, you won't need them anyways. Emulators don't support them anyways. For apps that support them, it's still better than using the touchscreen.
So I'm already happy enough for the rest of the gamepad. Having a real Dpad and real buttons is way better than using a touchscreen.
I never rooted my phone, no hints from me there, never needed to as Android lets you install everything just by checking "Allow 3rd party software" once.
Well, that isn't the point of rooting. It means you are logged in as root on the Linux system the Android system runs on. (And yeah, Apps can send commands to the Linux shell and I assume that most root apps work like that.)
That gives you many possibilities, like a Firewall app, that forwards IP requests of not-whitelisted apps to localhost (that means no ads! And there is an other app that takes care about ads (AdFree), it doesn't hurt to have both). Or you can easily backup and restore apps and their data (with TitaniumBackup). You can deinstall bloatware-system-apps. You can move apps to your SDcard you normally couldn't. You can mount the system partition with rw rights, theoretically enabling you to brick your phone...
Is it possible to keep the OS up-to-date by downloading an update?
Yeah, but an update has to exist.
If you want to wait for the official update by the manufacturer, you could have to wait pretty long, like I had to for the Froyo update for the HTC Wildfire. Also, the Wildfire won't get a Gingerbread update.
That's why it's wise to get a phone that already has Gingerbread, because you don't have to worry about getting Gingergread, and you can expect your phone to get an update to the next version.
Of course, there are also custum roms with user-made updates. It's kinda risky if you don't know what you are doing. And someone has to make them first, so it's still better to get one with the newest Android version now.