I would think that it would take a while for the granules to dry?
It has a blow-dryer, so once the granules are washed, they're blown dry. From what I've read, the entire wash/dry cycle takes about 30 minutes.
but yeah aside from getting the cat to use a toilet I can't see how the technology could advance past this
I can. If you read enough reviews, you'll see that thing is not without its design flaws. It uses a ton of water and electricity, and it takes a page from the inkjet printer manufacturer's playbook, and has proprietary, non-refillable cartridges.
In the end, I decided to stick with a regular litter box.