This inflatable kayak is a hoot! I bought one yesterday and did about 12 miles on the Truckee River through Reno in it with my teenage son. (Yes, I am incredibly stiff and sore, and he's raring to go again.)
First of all realize that this does not handle like a hardbody kayak. Close, but not quite. It is just a pointy rubber raft, after all. It likes to go down the river sideways or backwards, depending upon where the heaviest bottom sits. But, it can be easily paddled by one or two persons to float just like the real thing.
About thirty years ago I used to have a fiberglass kayak and went down many rivers here in the western USA. I've worn wool long underwear under a wetsuit to stay warm and have almost lost camera gear and food in rollovers. I kinda know how to handle a kayak.
This Sevylor should not be taken through anything greater than a 4, depending upon the skill of the paddler. It rides like a typical rubber raft through crests and holes. It might be fun to play with solo in standing waves, but it would be hard to brace into because there are no foot/heel rests. There is no way to stay in it in a rollover. You'll just get dumped out.
On the practical side, it only weighs about 23 pounds, can be had for around $140, inflates easily and quickly with a plunger air pump (sold separately), is easily portaged around the rough water, has a very shallow draft, is made from some very tough PVC, is comfortable to sit in for several hours, is easy to dump water out of, cleans off quickly with just a hose, and deflates in a heartbeat to be folded back into the size of a medium suitcase. For us, it is perfect - affordable, handy in the waters we frequent, easy to inflate/deflate/store.
I'm thinking of getting another one so that he can have his own, and so that I won't get quite as splashed-on from his flailing paddling. He can also tow old mom on the wide slow parts.