Overall, I found it to be exceedingly nimble for its size and it handled very well in fast water. It is quite broad, especially in the bow and stern, which would make it ideal for tripping on rivers. Unfortunately, we were only using it as a day tripper, and so without the load, we found its high ride was a beast in the wind on the open lakes. It had a mind of its own when it came to steering on open water, which was in stark contrast to the ease of control on rivers. We also found it to be sluggish on the lakes, especially compared to the other party we were travelling with in their OT Tripper.
I can't criticize this boat for being very good at some things, and not so good at others. It's really horses for courses, but for varied use, I wouldn't recommend it. For longer river tripping, both in rough and calm rivers, I think it would be an ideal boat.
Like most tools, it all depends on what you want to use it for. As a solo boat, I have found it nimble and quick when paddling Canadian style, even in current or wind. I'm not massively proficient when running solo, and it was noticeably easier than my OT. It holds keeled over on its side very well.
I have also run it tandem down class I/II rapids with fairly good success. It's in the class II that I would offer some caution. We were doing a 5 day trip and had kept the Wenonah more lightly loaded than the other canoes, but still with a decent weight and two guys. When hitting the heavier class II rapids, especially haystacks/standing waves, it would take on a lot of water. By lightening the canoe altogether, or trimming it to make the bow light, it did improve matters significantly. For serious rapids running, however, a longer Prospector will likely be beneficial. That being said, it does run very easily through rough water, and more advanced skills will likely help avoid taking on water (eg, hitting waves at a slight angle and slowing down the approach a little). It accelerates quickly and turns very easily, even when loaded.
I haven't yet done any longer flatwater stints with it, so I have yet to see how it handles in those conditions, but my initial impressions are good.
Overall, it's a fast, stable boat, with excellent stability and maneuverability that will serve you well in a variety of conditions.
On big water, it tracks quite well (make sure you adjust the trim) and glides very nicely. You can get up a good head of steam pretty easily with it. In rough water, it handles waves very well (I've had it on large lakes in 1-2 foot swells), taking on only spray.
For running rivers, it does track well, holding lines through rapids very well but turning can be a lot harder than a Prospector or other river boats. That being said, it is quite easy to move around rocks. Its 16 feet is useful for getting through bigger standing waves as well. I would have no real problem taking it through class I/II rapids (I've not yet risen to try class III yet). The Royalex is also quite ideal for slipping around rocks; it's very strong and takes a pounding well.
I would have one caution around stability: I think that the seats are pretty high up, which raises the center of gravity and makes the boat a lot more twitchy. In white water, this twitchiness can be quite disconcerting. I would definitely consider lowering the seats a little to adjust that. That being said, the secondary stability is very good.
Overall, an excellent all-round boat that will serve you well in a variety of conditions.