I'd have to agree with "cdw." The Hoback is alright for rafting when it's really high, but otherwise pretty ho-hum, especially in an oar rig. You also might find a couple of the really low bridges challenging at high water.
Usually, paddle rafters are ducking down below the tubes for two of them. The Snake, Grey's, are better, and if you're feeling good, the Upper Gros Ventre is still at ~3ft on the unofficial bridge guage, which is a great rafting level, although it is pretty continuous IV- to IV at that level.