The BBE is supposed to be a phase alignment device. The idea is that when a signal is amplified frequencies overlap and you get distortion. The BBE process is supposed to remove this distortion improving clarity and timre. It is not a compressor, limiter, expander or harmonic generator. The BBE like any other tool can be overused and much of an amplifiers distortion character can be lost with overuse. There are plenty of people here who would strap a bomb to their chest over this device without ever using one. The people who hate the BBE are often people with an amp fixation, who beleive the amp they own is so inherently perfect in every possible way that a BBE just makes it sound bad.
In my experience I have found the BBE is more useful after the tone generating sections, rather than in front of an amp and I would go with the rack mount, instead of the pedal. I prefer to put it dead last in a signal chain to clean things up. If not used in a guitar rig it is still usefull at the mixing desk for recording or live sound. I have used one for my guitar and stereo for nearly 20 years. There definately is something to it and it does work.