The take out at the Dirty Devil was not bad. We got there on labor day at about 4pm. There was no one else at the ramp which was nice. It is kind of a muddy area. There is a sort of ramp made of gravel that backs into the lake, but if you're not on the "ramp" there is quite a bit of mud. I was happy with the decision simply because we didnt have to motor the extra miles to Hite, and you're right on the freeway to Hanksville.
I would imagine that if there were more groups at the ramp, it could be a headache. There were only a few other cars there though, so I assume most groups were using Hite.
As far as Calirado's motor question, there river ends right below rapid 28 (29 was washed out, with no current). I forget the exact mileage (don't have my map on me at the moment) but it would be about a 25-28 mile row out with absolutely no current, and often decent sized Lake Powell waves. We camped at Ten Cent our last night, and had about a 30 mile day to take-out the next day which took us from about 8:30am until 4pm with a motor after the last couple rapids. It would probably take at least two to three days to do the row out without a motor, not worth it imo. I'd rather have the motor and spend most of my time in the canyon.