I have a quadraverb, and I think it is great. Used in mostly for guitar and always got compliments on my sound. I also prefer it over the midiverb, but that may just be me. It also has breathed new live into keyboards and samples.
To me, the reverbs and delays are it's strongest suits. Ring modulator is cool and some others. I don't think the chorus is that great, though I like it on acoustic guitar. The gates are lame, as is the EQ. The EQ can also get very noisy depending on how it is set up.
Very rugged to me -- have had it since it came out in about 1990-91. Also, very light and compact for a rack - not that deep. Though you have the lumo in line.