This piece of kit is great. I plugged it into the back to my 360, connected to my router....and that's it. Essentially, it's not quite plug-and-play, but it's very close.
I've given it 4 stars rather than 5 for 2 reasons - firstly, never pay full price for this - not because of poor quality but because £60 is a rip-off regardless, as it's essentially a piece of plastic and 2 arials. I managed to get this for half price (just under £30 in total).
The second reason is that the instructions aren't that clear. For example, when I put the accompanying CD in the drive, nothing happened. I couldn't tell whether the CD was duff, or what. Turns out, if you've recently been connected online (e.g. via a wired ethernet connection), you probably already have the necessary drivers and don't need the CD. Either way, a note to that effect would have been handy.
The signal I get from this is perfect - it's never dropped, slowed or anything else. I can get DLC at the same speed as a wired connection and I am several rooms away with walls and doors between me and the router. Whilst I like my gadgets, I like them to be easy to use, and this adaptor really is.
Highly recommended.