You are right leeneia - its the simplicity of the MD that is so appealing, but also the fact that with a combination of exploratory "noodling", plus a little bit of modal theory, there is so much versatility to unleash.

I was at an open air gathering of dulcimers (mountain and hammer) a few weeks ago, with the purpose of raising awareness. One bloke who was just walking in the park picked up one of our spare MDs, and in an hour he was picking out tunes; in 2 hours he was joining in the jam and was delighted with what he had accomplished. He had dabbled with guitar before but not for some years. I think there are few instruments that have that immediacy.
Do you belong to any online dulcimer forums? I know we are going off-thread here but its nice to chat with other MD players. I'd recommend Friends of the Mountain Dulcimer (its hosted by Ning). And if you are already on there then look me up (same user name)!