Have never had any hands-on experience. Most of the reviews that I have seen rave about the skewer-transmitter concept; and seem to be sort of mixed about the execution of the function/display and the stem-mount only configuration.
I had a good look at this before buying a Cateye CD300DW double wireless comp.
Apart from the lack of functions in the Mavic the thing that put me off most was the lack of resolution in the wheel diameter setting. From memory it only got you to within 10mm (1/2 inch) instead of the usual 1mm.
Having bought the Cateye I'm very happy with it. My only complaint is the small icon sizes in the display - things like avg, max, pace arrows etc are very small but the digits are large. The Mavics text is bigger.
Also you can remotes for the Cateye which you could graft onto your old Flightdeck STI buttons.
I use a Mavic WinTech. I liked the design of the integrated skewer as opposed to a fork mounted pickup. The display unit is large and easy to read however for the size I am surprised that Mavic did not incorporate an additional line of information.
The unit has worked flawlessly in the time I have used it and the wireless functionality has never skipped a beat.