My wife and I checked in for our flights to BZE tomorrow on my SmartPhone and the new functionality worked great, even with the need to enter my wife's passport information (she is on a reward ticket using my points and the passport info does not get pulled over to her PNR), changing seats and accepting an upgrade for one of the legs. I also like the functionality to have the boarding passes and receipts emailed for printing at a later time/date. The emails arrived in my inbox promptly.
I was using a TMobile Dash SmartPhone (WM5).