I've had a 600T for a good while now, maybe 8 months or so. Here are my observations.
The Good
1. Excellent case quality. Fit and finish is great. People complain about the plastic, but the finish quality and color is so close to that of the metal used on the case that it doesn't matter. It looks great.
2. Easy builds. Lots of room.
3. Cable management system is great.
4. 8 rear expansion slots instead of 7 means more room for expanded height cards.
5. Awesome, easy to remove doors/side panels.
6. Awesome support and warranty service.
7. Cusotomizable HDD bay positioning. You can completely remove the front mounted bays away from the intake fan.
8. Tons of room for radiator mounting if you're into water cooling, and tons of room above the MB for gigantic air coolers too.
The Bad
1. Weak fan controller. There are no official specs posted, but I've seen 5W max posted and I've blown mine running four fans that were rated 4W each.
2. If you plan on using Crossfire/SLI you need the verion with the open mesh side panel to let heat out. Mine didn't come with this and I had to purchase it extra ($30). This dropped my GPU temps 10'C (GTX 560 Ti's).
3. Stock fans are weak, but livable. At least they're quiet?
4. The case is big, I mean really big. From the front, looking at the center rectangle made of mesh, that's roughly the size of a normal PC. The plus side is that the size leads to lots of places to hide wires during your build.
5. Mine didn't come with a free bag of chips.
The 500R is interesting too. A bit smaller size and couple of added features over the 600T (turning off the LED's would be nice on the 600T).