So I was at the store today and tried it.
-Niiiice !
Really, I was blown away at the balls this unit added to the basses I tried it with : an EDA905 and some Modulus I couldn't even see the name of, so much the price tag was blinding me...

. I was playing through an Eden rig.
In any case, I find it hard to describe it otherwise : all of a sudden, the balls of the basses just increased in size. -The lows sounded much fatter, yet more precise. And diddo for the trebble.
So I immediatly thought I should sell a kidney and buy one.
But then I wondered : I went and grabbed a SA Bass Driver/DI unit, and tested it side by side with the Bass Exciter. And honnestly, if you just cut the Driver and Presence knobs on the SA all the way, put the Bass and Trebble ones at 12:00, then slowly increase the Bass control, you get pretty much the same effect that the Aphex unit does...
So I do believe it's a good unit. But maybe useless when you already own the SA.
Add the keeley Comp that I use (see related thread on that one), and I can do all that the Aphex does, and a lot more.
Still excellent for the buck I thought, if all you want is a ballsier tone.