I didn't find them to be too bad, and I was prepared for the worst because I have a bad back. My main problem was that the seats were kinda slippery. I spent the entire ride trying to keep myself from sliding down. I had to reposition myself 3-4 times during the ride to sit straight up again. I was in the very front, so I don't know if the seats further back have problems.
There was also no where to hold onto, which didn't help at all. The arm holds were back by my hips, which is a very odd place to have them. The back seats looked like it would be better since they have the bar going across the back of the seat in front of them. In the front you have a bar, but it's too far forward to hold on to.
Also for any women out there who wear skirts to the park, the front seat is great because you don't have to straddle anything. You're able to keep your knees together and remain fairly ladylike. The sliding down is a problem with skirts though. You have to keep pushing yourself up and pulling your skirt down.