If you like to play two handed, they are GREAT... I can't live without mine!

My layout is (from L>R)

Var1
Var2
Var3
Var4 (with auto fill ON)
Lwr 1&2 sustain
Sustain
Leslie Fast/slow

and then it's the only thing I need. But if you prefer, use regular sustains for LWR/UPR, and have Bass Inv, or Chord Hold, or any of a variety of things instead. But I prefer to NOT have Start/Stop or Break down there, just in case of an accidental miss-hit turning into a show-stopper!

It's honestly amazing how much better your timing and playing gets, when you don't have to take your hands off the chords and notes just to trigger a variation change or fill! Keep playing, and let your feet do the walking...