I have one. I haven't used it in a few years. They're fun until you get a big fish on and it is pulling you around. After that I got a 5lb wieght from a wieght bench for an anchor. I also didn't like having to reel big catfish up between my legs. You are also supposed to wear a life jacket while using one.
I've had and used float tubes for many years, and seen the considerable evolution in their design during that time, from round tubes that were an abomination to get into and out of, to the larger "U" shaped tubes, and now to what appears to be a trend away from float tubes (not entirely, mind you, because they still have their place) to a variety of pontoon boats.
I like mine OK, but even with the best fins (I have Force Fins) they still require a bit of effort on your part to move around some. Using oars in a pontoon boat is much easier.
Although I'm certainly not a fan of Dave Scadden, since you're close to Lancaster you might want to check out his innovatively designed boats (North Fork Outfitters) at the Lancaster Fly fishing Show this weekend to give you a pretty good idea of how float tubes and other 1-2 person fishing craft can be used in fishing situations.
I've had one for some 20 years. It's a good way to stay in shape, I found. I called it my pre-season "seal" training. I'd move from spot to spot. Once I got one I never went back to wading without one.
Good in a larger river. Although some use them to just sit in one area while they're fishing.
If you use one, you definitely should be a swimmer.