I do have the latest software version of the BBE sonic maximizer, I find it's only usefull if your guitar sounds muddy or cloudy in the first instance! esp in the low-mid frequency range, it adds 2nd and 3rd generation harmonics that improve the sound, and make it sound kind of phatter, and clearer in the bass and treble range, making the mids more balanced all round.
I use it more often on bass guitar and metal guitar parts than I do on anything else, from my experiments I've found that you have to be carefull how much excitation you add into the sound, as it can almost sound cheezy, and plastic if one isn't in a sensible mental state when mixing.
hope that helps you. :twisted: