Ostrich is much like beef in flavor, just very very lean. It really needs to be "medium rare" or "rare" for best flavor, not more "done" than that. I like it for the novelty, but it's not something I'd eat on a regular basis because I prefer fattier cuts.

Kangaroo is also tasty, though I don't recall anything memorable about the flavor. Just a mental flag of "Sure, I'd eat that again!"