We just got back from a three-hour Truckee River rafting trip in this boat. All in all, we're very satisfied with this purchase, and we think you'll do as fine as we did with it on a Class I river.
We're a family of five: two adults, two youngsters ages 7 and 5, and a 14-month old toddler. We ordered an inner tube from Amazon along with the Seahawk to make sure there would be room for us all. Once it all arrived, it was clear that we'd all fit inside the boat along with a jug of water and a bag of snacks, so we left the tube at home. The 4-person rating is reasonable, though if you were thinking of taking four adults on a fishing trip with tackle boxes and a cooler, I wouldn't recommend it; it would soon get uncomfortable.
The river this morning was mostly Class A (requiring us to paddle a bit) or Class I, with a few sections of very easy whitewater that might barely qualify as Class II. At those points, we dragged ourselves over rocks once or twice, but I didn't feel that the vinyl threatened to rip open. Along the way, we encountered many rental rafts, which were closer in style to the RST Marine Navigator II 500 available on Amazon. I felt that we were well-prepared, and their rafts were overkill, for the class of river we were on. In other words, on a Class I river you won't feel embarrassed to be seen in this boat.
The oars are adequate. It is fortunate that they float. They're short, and the leverage isn't right for river rafting when they're in the oar locks. We ended up combining the two into a kayak-style paddle, which worked well enough. The gear pouch will stop splashes from the oars, but it's nowhere near watertight. Put your cell phone in a Ziploc bag, preferably with a chunk of styrofoam so it'll float. The boat comes with two inflatable cushions that look ridiculously inadequate, but they were actually nice to sit on.
On disembarking, the Boston valves made it easy to deflate the main two chambers, but as many other reviewers have noted, the floor has a pool-floatie-style valve that's cumbersome to deflate. We strongly recommend taking along a Coleman rechargeable QuickPump (again, with a suitable Ziploc bag enclosing it) to flatten the floor at your destination. Once all three chambers are emptied, you'll find that you can easily roll the boat into a 16-inch diameter, 25-inch length sleeping bag shape. Consider buying a duffel bag, too; unlike some Intex models, the Seahawk 400 doesn't include a bag. The deflated boat is light enough for an adult to carry a short distance.
One worry was that the Amazon pictures show the green 2008 model (880-pound capacity with motor mount support), but the description is of the blue 2007 814-pound model. We ordered directly from Amazon, not from a third-party seller, and did receive the newer model as expected.
All in all, a great value. Next mission: attaching a trolling motor and cruising along Lake Tahoe's west shore. :)