I've talked with people who use the Keith McMillen Soft Step controller, and they generally report that it's pretty difficult to make use of all the multi-axis controls on each pad, and that there isn't enough travel or resistance to make fine adjustments. Those are very flexible and powerful MIDI controllers, but I think there is definitely a minimum size for a pedal to be really effectively useful on stage. I'm 5'6" (shut up. I'm not short. I'm FUN SIZE!) and I find the Mission controllers to be pretty useful; they're the size of a standard Crybaby wah. The down side to the Mission controllers has been noted by several forum users: they tend to flop down to the toe-down position, even if you adjust the nylon friction loop inside them.
The new EV-1 pedals are MUCH easier to control when standing on one foot, and they have enough travel to be useful for fine adjustments. I've experimented with some alternative continuous controllers like the Hot Hand, and ribbon / field sensors. For me, the "gas pedal" type controller is more intuitive, and a bit of physical resistance plus longer throw makes it much easier to walk up and put my foot on the pedal to make an adjustment without those dreaded "I barely touched it and it maxed out my volume" incidents.
