I am in the market for a B&M megashifter myself but just blew the cash tonight at Autobarn Cranbourne 20% off sale. Just saved myself $220 which is a nice discount for $700 worth of Pioneer head unit and speakers.
If I had the cash. I'd buy it. Provided it had the linkages to suit a C4 auto and had never been opened/installed. Also they have fatigue problems on the cables (short and long) and shifter knob thread.