I've used a Versa Climber. Thing kicked my ass, so I came back and used it again at a lower level, still kicked my ass! I like that it works me that hard, but oddly enough I find that thing to be the most monotonous machine even over walking on a treadmill.

Weird but true. That's why I didn't use it much while the gym I was at had one. Then I moved gyms where there wasn't one for 3 years, and now I have access to them again. Maybe I'll be brave and jump on one again, one of these days.