I have a Morley wah but to be honest dont use it a whole heckuva lot. Its got a sorta squelchy sound and seems to work better in the upper registers than in the low low bass realms and is really quite a pleasing sound but I have yet to use it for anything other than playing Cliff Burton bass parts.. he used a bit of wah with Metallica.
I have used it in funky jams but have yet to record it.
It is an optical system so switches on when you put your foot on it.