I rented the Moenkopi Whitesell for my trip last May, there is some discussion about my trip over on SOTP Forum.
The boat is obviously quite old but seemed pretty well spot on to me, it has even been fine tuned to deal with the afternoon head wind in the canyon

My swim count is in the thread, I think it was 9 paddling downriver (one of those on flat water) and one surfing a wave - I still have no OC1 roll!
Most rapids are easy because the essential move is at the top, in fact you often set up on the flat above to miss the problem feature, but as noted it is the chaos below that makes it hard work. There are a few trickier rapids depending on recent changes and levels - I couldn't visualize a line I had any confidence of making on Upset or Lava so portaged and lined them.
If you rent the Moenkopi boat I'd advise taking spare anchors and glue with you, a couple pulled off on me and there was sand in the glue suggesting poor quality field repairs in the past. I forgot to take glue and the rafters didn't have the right stuff so my repairs whilst properly cleaned up, might not last either.
Seriously, apart from needing some maintenance the boat is ideal - I was virtually an OC1 novice when we launched (owned an Ocoee for 5 years, paddled it once on grade 2 and spent some time trying to roll it, unsuccessfully), but found the Whitesell very easy to get used to and quite forgiving. Sometimes I wish I had one here instead of my Ocoee!
Jim