I had my first really great dragon fruit the other day courtesy of a friend with a very nice tree/plant or whatever you would call the crazy beast that grows dragon fruit. She refrigerated it so that it was cool and crisp. I could definitely see eating more of these, but only if I can get them straight from the source. The ones in the supermarket here look like they have been in the back of a truck for a couple of months (and are something like 6 dollars apeice.)
I gave a slice to my daughter who said, basically, "this doesn't taste like anything." She then went back to eating her apple.
My mother has a HUGE prickly pear plant. I have had prickly pear margaritas, so I think the flavor is nice. But I have never done anything with the fruit directly. This nice dragon fruit inspired me to crack some open next time I am in her back yard and figure out what is what. This recipe for a prickly pear vinagrette might be a good place to start.