Hi soundxplorer, what a coincidence, I've been thinking about an expression pedal too. I just decided to go ahead and order a Moog EP-3, which arrived today.
I've tested it just now and it seems to work great with the Pro 2. There's a trim pot on the side of the pedal which adjusts the range. With it set to maximum, and with the Pro 2's mod amount set to 127 aimed at Filter 1's Cutoff, the pedal actually had too wide of a range. The filter was just going from one extreme to the other and the pedal seemed too sensitive. Lowering the range on the pedal's trim pot helped me dial in to the filter's sweet spot and I got some rockin' "wah wah" action going on.
So I'd say it works great and has plenty of range. I recommend it.