I purchased this to add wireless connectivity to my Raspberry Pi running OpenELEC. My intention was to have the Pi sit in my second floor bedroom and stream media (movies and music mostly) from the HTPC running XBMC downstairs.
Upon plugging it in, I went to the settings screen in OpenELEC and entered in my wireless networking information. I rebooted for good measure and went to system information and found that it had no IP address. After verifying my wireless settings and rebooting once more, I still wasn't connected.
I tried a boatload of things, including installing RaspBian, RaspBMC, different versions of OpenELEC, various command line voodoo, disabling Wifi authentication, etc. None of this worked until I used a powered USB hub, and then it connected automagically. I was simultaneously relieved and frustrated when it worked. Relieved because it finally worked, frustrated because I spent so much time with it.
Now, several people have said that this doesn't need a powered hub for the Pi- which is actually why I bought it. My personal experience was that it did. I have seen things from other people about having to change their power supply to make Wifi adapters work on the pi - I didn't have another to use. Just keep that in mind that if you have trouble, try a powered USB hub before you tear your hair out.
With the Wifi now running properly, I took the Pi to my upstairs bedroom and set it up. I had previously verified that 1080p movies on the wired LAN ran without jitter or buffering. Playing with it on wireless, I found that I had to set my video streams to transcode to 1mbps 720p in order to stream without buffering. I was just happy that it was working, so I was OK with the quality drop.
If you are looking to stream high quality media over this I would suggest one of the other 300mbps or even 450mbps adapters available online. If you are just looking for a cheap, low-profile wireless adapter for web browsing, this should function perfectly.