My experience mimics khuon and is positive towards the Flightdeck. The almost ergo-perfect built-in buttons are fantastic. I only bump the buttons when wearing winter gloves and all that happens is that my readout changes from one readout to another. It has never stopped on me. Cadence and gear indicator haven't let me down, either.

Shimano's manual is none to user friendly, so don't think it's the answer to all of your questions!

The new Flightdeck with altimeter and HRM sounds like a nice upgrade, but I understand that it's quite spendy.