I want one (the bigger the better), but I totally can't afford it at the moment, little kids, our house needs attention, etc... My wife's not the camping type, though I could probably convince her on some of the destinations if we could carry some of the "comforts of home" with us. I could see a pop-up camper getting used enough to justify the cost, and maybe upgrade later, depending- I know we'd get more use out of it than a boat, anyway.
In other words, you're not crazy, I want one too. Good idea on renting one first, though- I'd probably try a couple different trips (short with just a couple folks, long with a bigger crowd and/or multiple drivers) in one if I was serious about buying, just to see how it shook out.