For the People with a Qtron+ there is an effects loop built into the pedal so you can run your distorton through and it is MORE than perfect. just like clean EF but with distortion. I run mine outside the loop and have success too, but you can run the octave, whatever and get clean mixtures of the EF and other effect. Its brilliant, no sensitivity problems. I noticed some people like the original Qtron rather than the plus, man better improvements in the Q+ imo with that upgrade alone. I liked the mutron III when I tried it, but like them all they need to be adjusted properly,and don't remember it being that much different than a Qtron. I agree with putting the Qtron+ especially against all others, and there are a few great EF's out there. If my Qtron+ breaks, I will buy another. I'm tellin' ya the built in EFX loop is the solution for ultimate compatibility if you use it for other things than Garcia.
I tried the Boss AW-3 an it had some interesting settings, but not very usable live and not very consistent. They should have stuck with the Twah for a usable design. I have to say I returned mine that ASAP. You CAN get an OK classic EF tone if you work it, but I prefer a true bypass if I can help it. cool thread for a person shopping for a Envelope Filter.