Having switched to the Xperia from an HTC phone, I cannot help but notice how awful my new phone's keyboard is. Writing text messages with it is a real major pain in the butt. I can forget about composing emails because the buttons are layed out in such a way so that it is impossible to tap the correct one. I've used many different touchscreen phones, but this is definitely the worst one I have ever come across.

I am on the lookout for alternatives, but I am really dissapointed with the SonyEriccson keyboard and UI in general.

I am a big fan of HTC Sense and that type of keyboard. It's just much more agreeable to me. I think it's the best Android keyboard out there. But since you are stuck with a SonyEricsson you should definitely invest into a keyboard replacement app. There are so really good ones out there on the Market.

I am with you about the keyboard problem. it's a real bummer to try and type on that keyboard. I can't tell you how many times I tapped the period when trying to type the letter m. it blows my mind.

Try this out: http://www.androidpit.com/en/android/market/apps/app/com.dasur.slideit/SlideIT-Keyboard

I can only highly recommend it. It works really great and savey you a lot of time. I wish it came standard on new sony ericsson phones.

I've used the SonyEricsson Android keyboards and to be honest I found nothing wrong with them. They aren't any worse or any better than the rest.

I was going to recommend using Swift, but I just noticed that it's been deleted from the Market ;( very strange

I recommend Swift Key.
Easy to type.