Digging a little deeper, I discovered that it was possible to transfer the small jpeg file across to the iPad without the additional NEF. This was much better. Images zipped across from the Eye-Fi card and on to my iPad in the blink of an eye. I was getting somewhere. The almost realtime review of images using the iPad transformed my image evaluation process. Great.
There was however one further fly in the ointment. Powering the Eye-Fi transmitter in the card really hammered the camera battery. Taking a spare became a must, especially on a full day shoot, miles from anywhere. I clearly needed to dig a litle deeper to see if the power requirement could be minimized.
Eye-Fi cards have been around for some time. So much so that my Nikon contains a configuration choice that will either enable or disable wireless transfer. What I generally do is take a few images with Eye-Fi transfer disabled. I then switch it on to transfer a batch of images and review from there. This will not be suitable for you if you are capturing a broad range of subjects. Its your choice - but at least you have a choice. I would recommend powering the camera off when not in use. You will drain both you iPad and camera batteries if you dont since the card and iPad are constantly communicating with each other.