I'm on the yahoo pumpmoms group, and a couple of the members there have tried it with mixed results. Apparently the company is still working out a few bugs, but are more than willing to send new parts or even an entirely new pump if a mom is having a hard time with it. So at least their customer support is good.
One of the members said she couldn't feel the letdowns (she usually uses a Medela Classic) but was still getting as much milk as she normally does. Another member did not have good results and wasn't sure if it was just because she was overly endowed or whether she just didn't have it on right.
I'm curious to see how it goes in the long run. I'd love to be able to put it on and leave it on, especially on the weekends. But I tend to have a low supply anyway, and would hate to use something that was only going to make that worse.