The IS seats were a real hot item in Automobile magazine's "long-term test." A couple of the editors bitched about them and others raved. Just goes to show ya...comfort is a very subjective thing...no butts
I've had mixed experiences. Some 6 hour trips my legs go numb, but recently I drove for 7 hours, and felt great the entire way. I think I may have found a perfect setting for it (now if they only had memory). I wouldn't trade it in for a softer seat though, as most of my driving is short and curvy, and I love the support. Too bad there isn't a way to swap out for a softer seat for the longer rides.
No BS I drove from Dallas Texas to Washington D.C. without stopping for count'em 22 HOURS. With the occasional piss break and caffine fix. I did not have a problem with them at all, i am 6'1" about 220, my girl on the other hand who is 5'6" (and very light) bitched about them off and on. It just matters how you have it set.
I happen to love the seats. I think it's because they simply fit me right. They are very contoured, and firm so if they didn't fit, one could understand why they are uncomfortable. I'm 6'1", about 215.
The fit of the seats was one of the first things I noticed when I got in...like a glove!
I took an 8 hour trip in the IS and my back was killing me by the time I got to my destination and my butt and legs were numb. It seems like the taller/heavier people are more comfortable than us shorter/lighter folks (I'm 5'4"). My fiance is 5'9" but he's pretty thin and doesn't have much padding and was complaining about the seats also. My sisters were complaining about the lack of space in the back seat but who cares about them.
I'm 6'4" 225 and the only problem I have is the lack of lumbar support. I don't think I could drive it for more than an hour or two without some sort of pillow. Even my Nissan Pathfinder had a manual support you could adjust.