Just in case anyone here has a 5.1 theatre system that has wireless remote speakers (like many of the Sony models), be careful how close you put your Mini to it. When I first set up my htpc, I had the mini, cable box and the Sony 5.1 components right next to each other. I was getting terrible wifi speeds and couldn't figure out why. I had my macbook sitting a few feet away and was doing various speed tests and the mini would get around 7 mb/s (and dropping packets) while the macbook was getting 15. I called apple support and they thought I might have a bad airport card in the mini so I took it down to the genius bar and it was getting close to 25 mb/s there. When I got home, just by chance, I moved the mini back a bit and it started connecting faster. It's now about 3 feet behind the other components and I'm getting around 23 mb/s.
Rule #1. Be careful where you place your mini!
Rule #1. Be careful where you place your mini!