Thanks for the great replies. I'd like to start by pointing out that, despite evidence to the contrary, I do know how to spell "Cadillac." I guess I need to narrow it down to the bikes I'm most interested in, then go into the relevant shops and ask them to adjust the suspension for my weight before taking another test ride. I weigh 240 lbs, and it sounds like it's not reasonable to assume that the bike will come out of the box configured for my weight. I'm not considering any full suspension bikes because I'm certain that I'd compromise strength, cost, or weight, or some combination thereof, and the extra performance isn't warranted for my riding.

I'm not hardcore. I don't have hills here, so I can't ride down them. It's just some nice, careful riding, with an eye to not getting hurt and minimizing damage to the trail. I'll ride for a long time never breaking 10mph, and it's rare for me to hit 15mph off road. That said, I prefer a slightly more aggressive position because it makes me I feel like I have better control of the bike at very low speeds. Right now, I'd estimate that my saddle is about three inches above my bars, and it's pretty comfy for me.