Vantaggi
If you happen to be deemed a "rock star" for any particular year, the bonus compensation will be very nice indeed. Benefits are definitley nice if you have a family. Everybody in the world has heard of Microsoft, which can work for you (and against you as well). Company events are usually pretty good - I particularly enjoyed TechReady every year. Great place to learn about other Microsoft products that you may not have any prior experience with - lots of internal resources to leverage when you want to explore something new. Lots of smart co-workers - as long as you're not management, you can almost guarantee that your peers won't be idiots.
Svantaggi
Extremely likely that the quality of your work will have exactly zero impact on how you are perceived (and rewarded) by management. It's really just a popularity contest, and there aren't any checks and balances on this process. You could be the smartest guy on the planet, delivering the most amazing solutions, generating nothing but love from your customers, but if you didn't happen to work with your practice manager at his previous company, or don't golf with him, etc - you can probably forget about recognition. Seriously, this isn't sour grapes here (I was actually pretty well rewarded), but the VAST majority of smart, hard-working people are ignored at best, and taken advantage of at worst.