I interned for Microsoft from 2010-2011 as a campus ambassador, but never visited Seattle and only spoke with actual Microsoft reps 1-2x during the program.
Our marketing initiative was to support the Windows 7 operating system. Responsibilities included giving demos to students on campus, distributing free collateral (bags, hats), building buzz on social media about Office products, and of course reporting it all online in a private ambassador community.
The stipend was decent ($700 every 7 weeks) but the perks were the real benefit -- I got a $2,500 Sony Vaio Z Series laptop, carrying case, Zune mp3 player, Xbox, games, etc. As long as you completed the program without getting fired (several people were), you got to keep all the stuff. In addition, they gave us Microsoft branded credit cards that we could use to buy pizza and drinks for Xbox LAN parties we hosted.
What I didn't like was how little we communicated with the Microsoft team and how rigid the quotas were for weekly demos and photos. If I recall correctly we were expected to demo 40 students per week, even during Winter break / holidays.
When one student asked about how to maintain the quota during breaks, they said we should "visit an old high school or community college" to hit our numbers. That sucked big time and I think most people faked the surveys during that period.
Looking back I probably wouldn't have conceded to their expectations if it were a smaller company, but Microsoft is an incredible name to put on your résumé and I've leveraged that opportunity to get multiple gigs at tech startups. So, there's that.