I have two inflatables (one pontoon and one kayak). Both are good boats, but they take forever to set up and I often get out and portage at some locations.
I ordered a 420x, and took it out with my wife. We live in Iowa, and are used to high winds. Well, I learned going downstream on a slow moving current into a 20-25 mph wind is not a good idea. There are times, when we were going upstream. Was that the boat's fault... no mine. The waves were 2 feet + high, and at no time did I ever have concerns. So I agree with others that these kayaks are not speed demons or masters of handling. What they are, is bombproof, extremely well built kayaks that come with everything you need.
I have to agree with the company that sold me the kayak. The deluxe seats will be better than the pro over half the time. If you plan on going on Level 3+ get the pro seats. However, with the inflation tubes so large, it was hard to paddle. Why, because the deluxe seat I sat in, and I was sitting on the floor. I re-inflated the seat while riding down the river no problems.
One other thing. The newer drop stick floor is awesome. You can actually stand (not recommended), but it is an awesome improvement. I saw one review "the master of all things, not the best at one." Well there is one thing ... The capacity of these boats has to put them at the top for extended trips to the backcountry.
I love this boat, and probably should have given it a ten.