I'd like to unlock my Xperia Neo V's bootloader, but on the other hand I don't want to lose my warranty. Obviously, that isn't possible. So my question is: Do Sony Ericsson's repair centres always actually check -- or care -- if the bootloader has been unlocked and if so, how often do they?
Impossible to predict what their techs would do. Theoretically they certainly can deny repair service on bootloader-unlocked phones, since it clearly says that you are voiding your warranty when unlocking the device:
Please note that you may void the warranty of your phone and/or any warranty from your operator if you unlock the boot loader. Sony Ericsson can then no longer guarantee the full functionality of your phone, and will not be responsible for any unsigned custom software being flashed to the phone after the boot loader is unlocked. ...
However, unlike the carriers (who 100% always check the bootloader status,) manufacturers have been known to turn a blind eye on this from time to time. For example, I've sent my Atrix 4G to Motorola for repairs twice after unlocking its bootloader. Both times their techs repaired the device, and even re-locked the bootloader for me. HTC is also known to be lenient towards repairing unlocked handsets.
You can always try calling Sony's support department and anonymously ask where they stand on repairs for bootloader-unlocked handsets. You may not like their answer though.