It's a TM and Microsoft is one of most aggressive corporations when it comes to acquiring TM domains.
If you do develop it, don't put any ads on the site that could point to any MS related field (software, computers), it may be easier to not put any (paid) ads on the site. (They can still take it though WIPO, though)
This domain is extremely risky but could have great benefits. Personally, I'd say reg fee since it is a highly risky TM domain.