I've got an ortovox M2. I've borrowed friend's other models and got this one because it's really easy to use and understand. It switches from send to recieve by unclipping one of the straps. Unclip the other one (in case you're searching and suddenly need to switch back to send because of another slide). It also picks up digital and analog signals both very well.
Anything you get will work, but it's absolutely useless unless you go out and practice with it. They work on kind of a doppler tracking pattern that creates an arc with intercepting waves........... meaning if you're getting a signal, the direction you're getting it from is not a straight line to the other transciever. Practice with it. Finding both one transmitter as well as multiples is a must and you should be able to discern more than one signal.
And don't wear it under 4 layers of clothing.
I got mine from telemark-pyrenees.com It's an english guy living in france that sells skis/backcountry gear etc for what's sometimes better than US wholesale prices.