The one thing this is SOOOOOO clear is that unlocking the bootloader through Motorola will void the warranty as you need to provide them phone specific information and they clearly state the warranty voiding clause before you accept the terms.
However, a number of members have stated that rooting voids the warranty. Is this an assumption or does Motorola state this somewhere? I would agree with this if it was always necessary (100%) to unlock the bootloader to root. I personally rooted without unlocking the bootloader and have kept it through the upgrade to JB.
Similarly does SIM unlocking void the warranty?
I've looked at Motorola's site and can't see much on what causes warranty voiding.