I never looked much at auxiliary gear for my guitar, always tried to spend little money for some hard hitting effects instead. That changed when I got the SY-1 a little while back. It's a fun sounding pedal on it's own, but from the get-go I was hooked by its hold function. Very clunky to use while playing though, so I got interested in getting an expression pedal for it.
I landed on this over other options because
a) it looks stylishly handsome
b) the "latch" mode
This allows the hold function to be turned on and off indefinitely by the B switch like you'd use any other pedal. The A switch either shifts your synth sound up an octave (so like a whammy pedal for just your synth, cool with the "close"-mode) OR acts as a tap-tempo for the seq position (can't seem to get any fast tempos by tapping though, not sure if it's this footswitch or just me). So if you have that pedal in particular and no expression pedal for it, I can recommend this. Hopefully I get some other "expressable" pedal for it soon.
And it really is simply handsome.