I read somewhere that if I am just updating to a later build of a ROM, I do not need to do a data wipe. Is that correct or do I need to do a wipe before going to Build 38 from Milestone 5?
If it's a small jump you dont need a full wipe (just clear cache partition and dalvik). the bigger the jump, the more likely it is you will need a full wipe (data, cache, dalvik). Or if the dev says so either way in the instructions.
for m5 to b38, you can probably just dirty flash (cache and dalvik), but if you have any problems you know what to do