I just signed up. I used it for an auction, I love the phone call thing. Makes sure I get the auction when I'm not at home (I was driving). I wish they coulda used a human voice for listing the phone options, since the synth voice was a little hard to understand the menu choices initially, but they have a listing of menu options on thier site if you need it.
Thier FAQ page says they have some sorta ebay certification, and that they make money with an affiliation with ebay where they get paid per bid from them. So thats why this is free to users.
Note: I had like 20 items being watched, I didn't want to get phone calls on all of them, so make sure you log in and pick which items you dont want to get phone calls on if you have a lot of them.
Anyway, this gets my thumbs up.