From my experience they tend to sound best when used in an effects loop rather than into the front of the amp (although that works too, but not as dramatic of a difference). To me it sounds like a loudness control for a stereo, in fact I would say it makes the tone more hi-fi. It's a cool, useful effect but not for everyone, try one before you buy if you can.
From what I've read about the sonic stomp, if you have a high quality signal chain (e.g. high quality cables, good amp, etc..) the sonic stomp won't be needed as much or at all in some cases.
I do own the pedal myself and it does add a little brightness and clarity to my sound, but if turned up too much it can give a synthetic type of effect, I guess this is what some peeps don't like about the pedal. In some cases (depending on the equipment your running through) it does indeed seem like taking a blanket off your amp, as many claim.
I have one, I'm going to be selling it soon. It's my understanding that it is only to be used in the FX loop (although I can't confirm this). With that said, I have a Mesa Boogie Roadster, which like many amps, sounds duller when the FX loop in engaged so....in theory I'd only be using the sonic stomp to bring it back to it's unadulterated FX loop bypassed glory.
I think that maybe it did sound a bit more "hi-fi" if you will, with the sonic stomp engaged; but not enough of a change that it's worth keeping. And my judgement may have been altered by my want to hear a difference.
In the end, I'm playing a highly tweekable quality amp and in a band mix the differnce of the sonic stomp is neglagable. I'm of the belief that if your amp sounds like there's a blanket on it, maybe a pedal isn't your solution.
I love my Sonic Stomp particularly for clean. Yes, it is right that the further to the end of your chain you can place this, the better you will fare. The ideal place for it is actually just before your power amp (in your effects loop).
What it is purported to do is sequence the frequencies of your signal such that the bass frequencies and the treble frequencies arrive at the ear at the same time. In the end what this means is that things sound a bit more "crisp". I notice it most with clean.
When I play clean (blues rhythm), I just leave it on the whole time. It sounds really nice on a good Fender amp (from my experience).
I don't use many pedals, but this one goes with me everywhere I go (I have two).
I use one in the loop of my 3120, it really does a nice job of improving the sound. Definitely "removes the blanket so to speak". Shop around on ebay as you can find them for much less than the going rate from the big retailers.
I think the Sonic Stomp is the smaller, lesser controls version of the BBE Sonic Maximizer. I picked up a Sonic Maximizer cheap on eBbay as "used" but it was brand new. I have been using it with my acoustic and running the direct out to the PA. It's a very subtle difference, but I really think the tone of my Taylor T5 is improved using the Sonic Maximizer.
I was wondering if there would be any benefit to trying it with my electric rig. I generally am just a hobby player, and I change my board up often and go into a Bassman RI or Twin Reverb RI. I might try it and see if there is any benefit.