building your own android iso is one of the biggest pains in the universe. I may have mentioned. I think I also mentioned how the build team had mostly stopped making specific builds for certain machines e.g. asus, and was trying to incorporate people's porting work into a main universal image, and this never quite happened correctly with the X-tablet stuff.
as a couple people have mentioned - if you can get the vanilla image halfway working, to the point where you can start messing with the startup scripts, this can be a lot easier/faster. (although becomes an annoyance vs. upgrading to later releases)
possible good news for x220t owners, but not so helpful for pre-x220 machines:
so, Intel has, all along, been contributing bits of code here and there to the ax86 project. the relationship is a little unclear - I think it was part because, of course, they're required to publish certain GPL related things, and part because they were happy to see a community they could push code to and see it tested, and how it builds/breaks/etc.
but the overall reason behind this was clear from the beginning: Intel was building their own versions all along. and now it's available:
(in fact they list builds dating back to 2012, but I feel this is the first I ever heard they were publicly available?)
any machine with UEFI and Sandy Bridge (or higher) should work ... in theory.
in the middle years, there are a bunch of "Generic UEFI" builds, and then the most recent 2014 ones go back to hardware-specific (Ivy Bridge, Haswell, Bay Trail).
if I can manage some courage, I'll consider trying either the 2/2013 x220t-specific build, or the 6/2013 Generic build. would love to hear anyone's experiences who dare to try this!!!