We are in the middle of a D6->D7 conversion and haven't settled on what to do for e-commerce yet.

I have seen enough of the demos to believe that the user experience will work, probably either way. Our D6 Ubercart experience is that the backend office processing sucks. That might be partially related to how we choose to do it in our office, but it is just plain hard to deal with.

I am about to bring up a Kickstart test site and see what the backend processing looks like. So far I have not seen many comments on other people's experiences as I really want to know what others do.