I believe this update will totally suck ... here is why:
it's a half assed update, no 16million colors for one, not multi touch even when they said 3rd party apps can make MT possible, why can't they? it will have bugs for sure
why?
simple, economics! SE is trying to perfect their own code like timespace and the other crap so the 2.1 is only to see if the code is fast enough on the current hardware, it won't be because with 16mil colors it will be a dog running on 3 legs, fat one at that.
what they will do is release it just before the new Xperia comes out with probably full 2.1 or 2.2, this will do two things ... will give users a taste of SE being quick to put software out and will cover them to some respect that hey we gave you 2.1 but the hardware is slow so buy the new Xperia and be happy
to them is a win win, they waited so long for 2.1 until new hardware will be out making it easy to wipe their ass with the X10 users, you want full 2.1 or 2.2 buy the new hardware! the X10 hardware has limitations they say specially for MT but hell the screen used in the X10 supports it, 3rd party apps can make it work
we will not see the X10 with 2.1 until they are almost ready to put out the new Xperia and with the "kits" all that means is that pending where the new X10 will be released has a lot to do where the 2.1 kits get released
the x10 = Satia no questions or dobuts about it, probably after the new Xperia they will start working on things but until they get their timespace and mediascape perfected SE will lie and delay things, it's the only thing they have to compete with SENSE and it's where the development goes, not on making froyo run on their handsets