I'm not here to give advice, but just to chime in with the same issue.
We also have a split-level ranch with a walkout basement. The basement has always been surprisingly dry, with mold/dampness confined to a few areas that had specific moisture problems (plumbing leaks, incorrect siding).
When we bought the house, the walk-out side of the house actually had pine boards on a homemade subflooring. That's still there. We've pulled it up in a few places during renovation, and not found any mold anywhere. However, the homemade subflooring is like a little home for mice and other critters... we found, um, evidence of that. The floor looks pretty crappy, with gaps between the boards to trap dust and contribute to a dirty (not moldy) smell.
So I'd like to get rid of that floor. Our contractor has given us a few options: tile (which would be pretty chilly, since there's no room to lay warming cables).
In Norway it's pretty common to lay warming cables in walk-out basements, then cover with tile. It feels DELICIOUS. It also really helps with the dampness problem. I haven't seen this done as much here, although I know a few people who have it. It does take up space in the floor and is easiest to do at the time of original construction.
The other option our contractor is giving us, is to lay a "floating" wood floor using an engineered composite wood that does not absorb moisture as much as regular hardwood floors. There's also the option of laminate floors.
I'm looking into the option of the floating floor -- it's "floating" because it's not attached to a subfloor, but fitted together like a puzzle, and then laid on top of some sort of moisture-resistant support pad. We would do this because there's not really room for a subfloor (the celings are too low). We'd rip out the one that's already there, and seal the cement floor with one of those water-resistant basement sealant paints.
There was an article about precisely this issue in Taunton's Inspired House magazine, August 2004 issue. How to turn basement into safe living spaces, new materials allowing you to put wood floors in basements.
Anyway, if people have thoughts on this whole issue, or any experience with the various kinds of basement flooring, I'd love to hear more!