Same situation here. I had an older Intellimouse Explorer USB. It recently started dying on me, so I called them up (it was NOT a toll-free #) but the people at Microsoft Tech Support were very friendly and accepted the fact that I knew what I was talking about so let me skip all the "diagnostic questions" and just gave me a number to call and a service number and that was that, they sent it out and I recieved it in like 4 days. Overall great service, if anything I think Microsoft may be TOO trusting, I could have easily not had a problem with my mouse and I could have still totally BS'd my way into them just sending me a new one. Oh well, they will eventually learn =)
Good luck.