Kernels not withstanding, the Xperia X10 can run Gingerbread. I know, because the guys at XDA have released basic source code which can be installed through Zdzihu's backup/restore util. It's slow, VERY slow, because there are as yet no drivers for it. However, it runs on the existing kernel.
So - I'm currently able to run 2.1 (SE), 2.1 (SE-lite, all the crap removed), 2.1 Custom AOSP, Jerpelea's current Miui edition (which has a bagload of potential) and 2.3. This phone gets better.
Pete (I need JD) Graham ************** Damn you! Use forum search!!.