i worked as a white water raft guide for the past 2 seasons, and we used NRS duckies both single and tandem versions in addition to rafts. they worked well enough to navigate up to class IV+ rapids, they are relatively stable, hold air well, and were very durable.
I've got an "Advanced Frame" solo inflatable from Advanced Elements. I used to whitewater kayak, and was skeptical at first, but have been very happy with it. It's stable, tracks well, and is easy to paddle.