So, seems like the Xulrunner nightly build service Brad Lassey was talking about is working already and i tried running some simple xul apps in it - they work, just like Fennec So, we now have another development environment if someone care about it (porting Prism springs to mind, that would be sweet).

You can find the latest Xulrunner here:
ftp://ftp.mozilla.org/pub/mobile/

I tested the one in the dep directory.

Crowbar here (tested xul app):
http://simile.mit.edu/wiki/Crowbar

Feel free to post other interesting findings. Check Fennec to see how to enable extensions for the app (though i don't know how you will use them

(the svg clock xul app doesn't work, seems there's no svg show support in this Xulrunner).