Yeah, the above post pretty much says it. On the U.Gaul most rapids end in a pool. On the Upper A most dont (at high flows anyway- which is when you wanna be there). If I remember correctly the 2 drops that are called class 5 (above Rockwood) have long sections of bouncy and fast class 4 following them immediately, with few recovery eddies. I chased some folks in a flipped raft last summer at peak flows and we chased this one lady for nearly 1/2 mile... We´d get her to a micro eddy near shore and then she´d just bounce back into the current. If she hadn´´t been the only one in the group with a drysuit on she probably would have died after so much cold water exposure, continued dunkings etc...scary. Also chased a boat for quite a while.
Also, at high to high-ish flows the run can be done in one long day or 2 comfortable, totally manageble fun days (ie: you can sleep in a bit, cook breakfast, wait for it to warm up a little). The area is extremely beautifull and well worth doing the trip in 2 days just to camp in such a cool spot.
If you know how to stay centered and not get squirted in bouncy and semi-pushy class 4 to 5 you could definitely get by in a playboat, but the water is cold enough that you wont wanna play much. Creekboat or a river runner would be the way to go for max fun in my opinion. Its just fun paddling a faster boat on that river and staying a little dryer, more comfy etc. Plus, you can surf those glassy waves that spuds cant catch . Definitely a must do though, so have fun!