The longest drive I've taken was about an hour and a half of continuous driving. I didn't have any problems with the seat comfort. Other than an almost complete lack of lumbar (lower back) support, I think the seats are great, especially with the Alcantera inserts on the SRT6 (keeps you firmly planted). If your lumbar support is overly bolstered, it is possible that someone custom modded the seats to add it in there. Natively, they don't really have much. I'm 5'10", 185lbs and found a comfortable seating position pretty quickly.

Rearward visibility is a bit low. I didn;t really notice this since my Trans Am had pretty much the same problem, but driving a rental while my car is in the shop, I realize how huge the blind spots are. As fformula88 referenced, at certain intersections where you have to check traffic to the right, you will need to adjust your approach angle so that you can see oncoming traffic. You get used to it pretty quickly.

If you like the car, but dislike the driver's seat, you can always have it modded or replaced.