Sony Ericsson finally release the unlock boot loader for certain Xperia Android phone models in 2011. With this happens, we could install custom ROM and other third party applications without looking the unlock boot loader tricks.
The unlock boot loader only happens on latest Xperia Android phone such as Xperia Arc, Xperia Neo, Xperia Pro and Xperia Play while for Xperia X10 Android phone series not included. Just notice, this is the official unlock boot loader while for X10 series, we could do this by follow instructions from other developer.
One more thing, even if you got one of these phone it should be SIM unlocked Smartphone as the carrier branded device are not allowed to modify. But hopefully the genius developers will give us a way around.
If you ready to unlock the boot loader, you may head to Sony Ericsson unlockbootloader website to get further details guide how to do this. You must have good knowledge regarding this technology and risks which happen if you unlock the boot loader because your warranty may void. If you fail to unlock boot loader for certain reasons, Sony Ericsson will charge you some bucks to repairing the phone even the phone still in warranty limit.
So, if you think unlock boot loader is not quite enough to give you some reasons to do it, just leave the phone as is like you get the phone in first time when you buy.