I gave in to temptation and bought this EQ after hearing various online guru's gushing about how uniquely novel it was, how it does what no other EQ can do, which is true, in part.
It's usual function is as a boost EQ, for emphasising certain mono signals, such as vocal, bass, lead guitar and synth lines etc, to stand out from the rest of the mix by boosting odd or even harmonics and the fundamental frequencies by means of a pitch correlation function that moves up and down the frequency spectrum with the audio, boosting whatever notes are passing through it. It works reasonably well in its default setting, but some signals can prove to be troublesome to get a 'Lock On', meaning adjusting the threshold and sensitivity are necessary. I find that using the High Pass filter to tailor the lowest frequencies of the signal can help in this regard.
As a general eq it is very good indeed, I particularly like the centre bands 'Harmonic' settings for making tracks jump from the mix, with varying degrees of severity. The normal bands are very 'Musical' in that they can be boosted or cut heavily without sounding over processed.
Graphically, the GUI is very good, the frequency spectrum works well to confirm what is going on with any alterations made, while its overall look is that of a quality tool.
'Pro's' are its quality sound, ease of use, great look with informative feedback. The Surf function is generally excellent and will make your affected tracks really stand out.
It's few 'Cons' are that it is expensive, (come on Soundradix, offer more in the way of sales and discounts!), Surf Mode only treats monophonic signals (though the plugin can be used on any signal in non-surf mode as a general EQ), it occasionally glitches with certain audio tracks and it has a very 'niche' functionality.
To conclude; I don't reach for this EQ every time, but when I do, I generally think I made a good choice. It occupies a very unique spot in the marketplace, works well, if not perfectly in its intended purpous. It would score four-and-a-half stars, if that were possible! Well done Soundradix, I look forward to trying their other products (maybe when they have a sale or some form of discount!) in the near future.