Bad move from BMW. The whole beauty of the 650 is that it has a SINGLE CYLINDER engine, with all the associated benefits of light weight, simplicity (apart from when you want to fit a Scottoiler - see thread!).
By moving to a twin, IMHO they are moving too far from the "jack of all trades" appeal of the current F range and hunting for a different audince. Maybe that's what the bean counters in Munich are demanding, but if they change to the twin the current F buyer would be a bit stuck. I see the other 650G series (G-X etc) as aimed at a different market....