IT WORKS! Installation via xRecovery.
Here's a mod of the AOSP ROM. What I've basically done is added a Gingerbread theme, add some Gingerbread apps and a few other things. It's based on version 008a of the AOSP ROM.
I don't have a Xperia anymore, but if people are willing to post some screenshots, I'd dearly appreciate that and include them in the OP.
If you like my work, you could consider buying me a beer:
I am not responsible for bricking your device! Your doing this all on your own risk. Please report the bugs via PM and do not post them in the thread.
Modified the Phone app, some other stuff. The menu-text is grey (I stole the correct .xml file from a Desire Z ROM), statusbar-background is black. Everything should just look a little more fancy.
Modified the status-bar, framework-res.apk to look a little more like Gingerbread.
OK it should be working again. The problem was probably services.jar
HTC_IME doesn't work for some reason, needs to be installed manually.
Camera drivers aren't fully implemented yet.