These have been in service at Madingley for a couple of months now (we used one on 21 May). Essentially they appear to use the same shell and guts as the latest railway TVMs. The major improvement is that they will take cards, give change and can sell you multiple tickets at the same time.
Can not remember if you could buy more than just a P&R return (as that was all we bought) but there is clearly scope here for future expansion, for example DayRiders, MegaRiders, X5 tickets, City Sightseeing etc.