I never thought I'd ever see one in my neighborhood, but I was riding this morning and saw someone riding one! From the looks of it, it could've been a Catrike. I couldn't really tell at the speeds we were going. He was opposite me. In hindsight, I should've stopped to chat with him a bit.
Last weekend, we saw another recumbent tadpole trike except this one was modded to be powered by arms rather than legs. The rider was way buff and had tons of upper body strength. Looking more closely, it was modded b/c he had lost his right leg. It's pretty cool that someone was able to mod it so that he can get around like other cyclists out there. The hills must be way tough!