The Tact 2.2x is a VERY good preamp, but it is slightly to the detailed and clinical side. If you want a lush, full tubey sound, this isn't it. But it's pretty transparent and let's the music come through. As an option, the Aberdeen power supply upgrade smoothes the treble a bit and it sounds somewhat fuller and more organic. A good PC helps too (I'm using a Concierto Violin).
To me, any slight (and subjective) deficiencies are far outweighed by it's advantages. When I first put it into my (previous) system and corrected the bass nodes, I felt like a blanket had been lifted from the speakers--the ripe and congested mids simply opened up with clarity and natural detail, and the sloppy bass was now tight and tuneful. Room/bass interactions affect more than just the bass.
I'm now using two double stacks of Linkwitz Phoenix subs (eight 12" drivers) and there's nothing like deep, clean bass extension to make things come alive. People tend to shy away, thinking that this is coloring the sound, but in reality, the room is coloring the sound and this brings it back closer to the original.
Sure, if you want, you can also use the room correction into the mids and treble if you want, and create correction curves that are more suitable to certain types of music/personal tastes. Sort of like tube rolling without the hassle. You can warm up the lower mids and roll off the treble to taste, without much penalty.
The optional DAC is also pretty good. I use it now for the subs, since I also have a Tact 2150 amp (which replaced Dodson and modded PT DACs and a Gamut amp in my system). But the internal DAC is a steal at the price--though you can do better for more $$.
If I wasn't interested in room correction, there are other preamps I'd buy first for the money, but in this case, I'll second the "once you hear it, it's hard to go back" line. That is unless you're using vinyl or SACD (which I tried but didn't think the A/D converter was in the same league, esp w/ the necessary downconversion).
There's a review in TAS #150, and some others as well (Hifi News, etc).