Note that when you book with MS, you need to tell them you are using developer points. They are managed by a different system. They will hold your room and send a paper request to get the developer points used. Your reservation will not show up online either. Note you cannot combine them with regular points. I have 1 developer point left, and I cannot possibly use i because of this! Can't complain too much though!
You can make a res with dev points and one with reg points and join them, but you can't pay for part of a night with regular points and part with developer points.
Also dev points expire one year from date of purchase.