The Sony Ericsson Xperia X10’s bootloader has been stubbornly hard to crack. The tight security has meant that the xda devs have had to deploy custom ROMs using the existing kernel. However, judging by recent events on xda, it looks like we may be moving one step closer in finally seeing the bootloader being cracked.
One of the devs called Bin4ry managed to use his own kernel to load a custom image, although there were a number of barriers including a lack of working touchscreen and USB. More recently another developer, jerpelea, confirmed that he was able to load a CyanogenMod 7 ROM using a custom kernel. There is still a long way to go, but these are definitely encouraging steps for the X10 community.