I've owned a Quadraverb 2 since they were 1st released over 5 years ago. I also have 2 other reverb units from the same era - a yamaha SPX-990 and a Digitech (can't remember model #, but it was the one with S-Disc, and was in the same price range as the Q2.)
Back when it was released, the Q2 was a reasonable reverb unit. And compared favorably with the Digitech and Yamaha. It sat in the middle ground of the market - not quite a Lexicon, but better than most budgets units (e.g. spx 90 mkII).
These days I'd recommend buying the Hyperprism suite of plugins from Arboretum instead of a Q2 (unless you *need* a hardware unit). The reverb on hyperprism is so much better than any of the hardware boxes I own that I'll never buy another one again.
By comparison (on lead vocals), the Q2's reverb is thick, heavy, dark and muddy. Hyperprism's is clean and dense, without cluttering up the mix with muddyness. It is truely stunning.
Here's an interesting little link: http://www.arboretum.com/reverb/reverb.htm
I consider the Hyperprism reverb better than the TC Electronic reverb plugin's (based on personal listening tests). After all, TC still want to sell their price-inflated M5000's, so their plugin had better not sound as good as their hardware! - and believe me, it doesn't...
Back to the Q2... In short I think this unit has had it's day. For the price I paid for my Q2 new, I could buy the hyperprism suite with 30 different effects, and have plenty of change in my pocket. There are better options out there now, check them out.