I just did a gig with a 3-Leaf Proton for the first time. Blew me away, actually. Very warm envelope sounds, plenty of bite to cut through the mix, but none of that "ice pick" sound that envelope filters sometimes give you. Plus it barely takes up any real estate on the pedal board. I think the recording of the show came out pretty good--I'll see if I can post a clip.
This is probably the 6th or 7th envelope filter I've tried, and I think I may finally have found a keeper!