I have one and as was mentioned, yes the transfer rate is slow. It depends on how big the photos you are putting on the iPod are. My girlfriend had a Canon 300D which takes 6MP photos and using her 1GB card it took almost a full battery cycle to upload the photos.
If you want to get these photos onto you Mac (which I am sure you will) you need to mount the iPod into Disk Mode and then import the photos into iPohot as ar as I can tell. That is a bit of a bugger, it is not very Apple like and would be great if it was autmatic when you connected your iPod.
The reason that I have one is that when ever I go away and dont take my PowerBook with me (not very often!) I can easily empty the camera and not have to delete photos to free up space. After all it is cheaper than a new memory card for the camera.
Bascially it is a good idea but Apple could easily turn it into a great feature by:
1. Allowing you to connect the iPod to a charger when you uploading photos
2. Making it easier to get your photos into iPhoto