Ok went out and bought one. Couple of notes from me. Works fine, just right for my application, which is taking photos and having the ability to see them on a computer / lap top screen right away. Just like Curt I'm not using it to automatically upload to Facebook, Twitter, etc. So cannot comment on that.
Install easy, put the card reader (supplied) and card into a USB port on your computer and follow screen prompts. You will have to know your Wireless Network Name and password to set up the card.
IMPORTANT: After you install copy all files on the card to your hard drive. You may see a screen prompt that says you can Format this card, don't do this unless you have copied the files off the card, you will loss all the install files and will not be able to reinstall this card else where. (Found this out the hard way, had to go back to my Wal-Mart and argue the fact and got my card replaced)
This card (Eye-Fi 4GB), WILL NOT SUPORT RAW / NEF FILES for wireless transfers. If you want to shot and upload RAW files your going to have to upgrade to the Eye-Fi PRO 4GB (Amazon $119.00)
Works across two cameras. I took the card, which I set up in my D-90, and put it into my D-3000, took a photo, and the photo from the D-3000 uploaded just like it was in my D-90.
I thought I had read in the Eye-Fi Forums, you can only install one instance on one computer, and file sharing across your network with the Eye-Fi card was not possible. Can't find the thread but here's the link to the forums:
Eye-Fi Forums • Index page
CF to SD adapter questions, you might want to try this forum
Eye-Fi Forums • View topic - CF to SD adapter
Overall I'm happy with the card. For right now I will only use it around the house, when I go out I'll uses my standard card because I' shoot a lot of RAW files outside the house for possible HDR photos. Only disappointment I have is that this card will not support RAW files.
If there is any misinformation here please correct me, thanks.