I bought a zero-effect last year after some years of tinkering with different rests. All I can say is, I probably will never use anything else. Although in pictures it appears bulky and complicated, when you put it on, it is just about the most simple and uncomplicated rest you can have, at least among rests with movable parts. There is no loss of speed or anything else to complain about as far as I am concerned.
I stayed away from conventional drop away rests, because I didn't want an extra string running somewhere, and if you caught the string on brush on the way to your stand and pulled it loose or broke it, you might as well go home.
My thoughts on it.