I have one and use it to boost my EVH 5150-3 head..I use it in the loop and its and always on pedal for me,something about it that brings the sterility out of the EVH and I guess just boosts the amps natural frequencies and fattens up the tone,it also has 2 DIP switches inside after removing the bottom cover and I have both mine switched to what I would call the "UP" position and my EVH sounds so much better with it like that.
I have no experience with the Echoplex so I have no info on it.
I have had my EP booster for 2 years with no problems ever,it just makes my amp kick ass ! I even used it with a SS Ibanez TBX 150H head and I had great results,but that head sounded badass for a SS amp.
I like mine a lot,and I even have bought a copy of it,and truthfully I think its sounds better and much less expensive.