Worthless, didn't work at all!

I had marginal wi-fi reception and bought one of these at Best Buy. I connected it up expecting to get "up to 600%" signal improvement but there was no improvement at all. It doesn't seem to amplify the signal either way as far as I could tell. When connected to the router there was no change in signal level so I moved it to the PC and connected it there to see if it would amplify the received signal but the level was actually a bit LOWER! I was able to connect with the wi-fi router before but with the unit installed I couldn't connect. It seems that hooking up the box and extra 2 feet of cable lowers the signal a little. I took it back to Best Buy and got a refund since it proved to be worthless. Some users complain of overheating but mine never even got warm, it's as if there was nothing inside the box but a switch and some LED's.