This is the best thing i have ever bought for my 360. My console was in my bedroom and the router downstairs, so i had to connect with the ethernet cable through my laptop, i was lucky to find a game on mw2 and FIFA 10 lagged constantly, due to the fact that the laptop triggered NAT issues.
Now that i have this adapter, the lag on fifa has been reduced to a minimum, and on mw2, i can find 30+ good games instead of 1 or 2. All NAT issues have been fixed and my xbox live experience is at its best.
55 quid well spent, i recommend this :D