I see this thread is old but I finally decided to tether my Xbox 360 last night through my rooted DroidX. I also have the Xbox 360 Slim with built in wireless. I was able to play Halo Reach online with ease, in fact I was the host connection. I was even able to watch Netflix it was at the second to lowest resolution which didn't look to bad on a 26" 720p tv. I racked up over 1GB between xbox updates and 4 episodes of bones and one game of halo. Surprisingly the game of Halo racked up the least amount of data. I will be playing Live this way all the time.