I have to say that I looked at this device a while ago when I realised that Nikon just wasn’t going to put wireless on a lot of it’s cameras for a while yet. It also offered way more possibilities than the Eye-Fi devices did, even though they were handy. I still use them on occasion, for a quick transmission of photos to show someone. The Nikon Wifi units such as the WU-1B or WU-1A themselves seem of little use to me in their current incarnations, and better units cost significantly more but with no better functionality until you reach the $1000 price range.
The best feature for me is of course the iPad application. It allows me to stop cramping myself into some ridiculously tight spots.