It took more than a year, but the devs at XDA-Developers have finally made it happen. The Xperia X10 boot loader has been bypassed, which means that installation of custom kernels is now possible.
There are already dozens of custom ROMs available for Xperia X10, including some pretty decent FroYo (Android 2.2) and Gingerbread (Android 2.3) ROMs. However, the locked-down boot loader meant that all of them had to use the official kernel (2.6.29).
Although Sony Ericsson has announced that it will be allowing power users to unlock the boot loader in the near future, users of older Xperia models (Xperia X10/X10 Mini/X10 Mini Pro/X8) won’t be getting this privilege. Thankfully, Zdzihu, of the FreeX10 fame, has managed to load a fully working custom kernel. He has released an alpha kernel, which is a modified version of the stock 2.6.29 kernel, as a proof of concept. Among other things, the patched kernel does away with the artificially imposed frame-rate cap, implements netfilter, and reduces the voltage to conserve battery.
Quite obviously, the alpha release of the modified kernel isn’t suitable for daily use. However, this does open up a lot of new possibilities, and gives the developers more freedom. Zdzihu will soon start working on porting the Gingerbread kernel from Xperia Arc. In the meanwhile check out video demonstrating the enhanced fluidity of the interface with Z’s custom kernel.