^^^ This
I have an Eye-Fi card. I never use it.
I bought it thinking that I'd be able to pair the camera to my iPad (I can) and transfer photos to my iPad where it's easier to review and ... if I want I can process it on the spot. But the reality is that I have to wait quite a while from the moment you snap the picture until it finally shows up on the other device.
To save power, the radio switches off when not transferring an image. The camera and card wait several seconds to see if you're going to take any further images and, if not, it begins the transfer. This means every image -- regardless of size -- has a bit of a delay until it switches the radio on and completes the transfer. If you shoot RAW, the transfer itself will take quite a while. You must not do anything with the camera while the transfer is occurring or it will stop the transfer (you can't transfer and shoot simultaneously... it only seems to want to transfer when the camera is idle.)
If you're back home and want to transfer your images, it would be much quicker to do the transfer by inserting the card directly into the computer or using a USB cable.
While the cards work... they are slow to the point that they disrupt the pace of your shooting to an uncomfortable amount. I was hoping for something that allowed me to shoot without really thinking about the transfer and just have the transfers going in the background, but it doesn't really work like that. You shoot... wait, wait, wait, wait, review... shoot... wait, wait, wait, wait, review... etc.
incidentally, it's my understanding that earlier versions of card or camera firmware allowed the card to keep the radio on and spooling continuously... but this killed the battery much more quickly. They now toggle the radio off to extend battery life.