I've tried the treadclimber... it's a very wierd machine. Some people love it, some hate it. The idea is that you can use it as a stepper (up / down) or as a treadmill (long running strides). But to be honest... .... well, just try it out first!
Treadmills vs Ellipticals? Depends what you feel most comfortable using. Ellipticals are better for you (less jarring on the joints so your knees last longer). But personally I prefer a normal treadmill... I like the way that the deck keeps moving beneath you so you just have to keep going. With an elliptical, I find it too easy to slow down.
E.