I bought this Eye-fi card for a new Nikon D3100 I gave my wife for Christmas. It came with a USB card reader and simple instructions - basically "Plug it in". The card installed its software, downloaded updates and connected quickly to my wi-fi network. My wife logged it into her Facebook account, then we put it in the camera and started taking pictures. Within a couple of minutes of taking each picture, it was on Facebook for all her friends to see! Then we figured out that we needed to set up selective upload so that only photos you want to share are uploaded to Facebook. Either way, every picture we take at home is immediately stored on our computer, and ones taken away from home upload as soon as we get home. Much better than our old system of uploading our pics when the card filled up - you know, in the middle of our daughter's dance performance or son's karate tournament.
A nice feature of the Nikon D3100 is that it has built in support for the Eye-fi card, so it actually shows when it is connected to the network and will not shut down until the transfers are complete.