One fundamental advantage of the Jobo is the fact that it only records positions when you press the shutter button...it does not have hundreds of thousands of extraneous positions in a log file which rely upon synchronization of the camera time and GPS time in order to pair the position to the photo.
The downside is the need to mount the Jobo in the hot shoe (or, I presume it has a capability to be tethered to a camera with a PC cord, which itself is bothersome).
Yeah, I think its actually a neat idea, but using the hotshoe is a deal killer for me. Given the size of a GPS log file, and current software that easily allows time syncronization, even thousands of waypoints and time mismatch isn't a big deal so long as you can do some math. Canon's grip+GPS solution seems overly cumbersome as well, I need a grip + GPS unit... when I could just leave the GPS unit attached to my belt or bag and sync later.
While I like technology, I also like simplicity. Right now for my use for geotagging it still seems a good GPS unit and tagging images later is still the best solution. I know I personally would rather have built in GPS functionality than a print button, but hey =)