Well, I received the Wampler Nirvana Chorus and it is an excellent product! I'm really, really enjoying this chorus. I've been on a "chorus quest" over the last few years and this thing has really answered the mail in a lot of respects.
A couple findings:
Build quality is exemplary. Excellent fit, finish and function. The housing and knobs are all excellent quality. The feel of the switch and knobs is excellent. When turning the knobs, the action feels super smooth yet firm. It would take more than an accidental bump to move the knobs when you've set them.
Unity gain: Having a volume knob is awesome. It's really nice being able to volume match your clean and effected signals. When set, I can switch back and forth with no boost or loss of volume. VERY nice!
Background noise: It is a very, very quiet pedal. I could only manage to get a tiny bit of background noise when I maxed the "tone" and "volume" settings when I had my amplifier turned up VERY loud.
Full range tone: The chorus effect covers the entire range. Low B to plucked harmonics all had the effect. Definitely no loss of tone, effect or volume.
Versatility: Here's where this thing is worth the money IMHO. With the multiple switch settings (I haven't even messed with the Vibrato side of this pedal yet!), the tone knob, and depth and rate knobs I've already discovered and dialed in several usable chorus tones from smooth and warm to bright and shimmering to deep and intense to downright outer-space sounding warbles! It is NOT a one trick pony!
This unit is definitely in the "you get what you pay for" realm of gear. It may be a little spendy, but so far I really think that this level of quality, tone and versatility is worth it.
Just my thoughts on all this of course!
I'll post more thoughts when I get some more time with it.