After ICS SDK released there’s so many devs trying to port it to their android smartphone or tablet, after HTC Desire Z / G2 successfully boot ICS now another developer also working to port Ice Cream Sandwich 4.0 to Xperia X10 smartphone from Sony Ericsson, you have to installing a Custom ROM if want to run ICS since SE will not release official ICS for x10. They might try to dump SDK system image and try to port it to X10, they believes this will work since another developer from xda-devs with username aZuZu successfully port Honeycomb SDK to X10.
Porting ICS from SDK is not easy, and need a hard work as SDK isn’t designed for real device, we should wait Google to release ICS source code which designed for real device. If you need more stable release you can wait CyanogenMod CM9 build. Are you have no idea if your X10 smartphone can run Android 4.0 update ? I think your smartphone can run it, since ICS minimum requirements is 256MB of RAM and your X10 has little bit more (384MB RAM), also you might want to buy Xperia Ray which will get official ICS update from SE. If you can’t wait to feel ICS-look in your phone you can try launcher apps or maybe installing theme.