T-Bone is a 'tilt' or 'slant' EQ. A tilt EQ raises the amplitude at one end of the spectrum and lowers it equally at the other. I find them really useful for doing quick and dirty adjustments to overall tone, and for 'pushing' sounds into a more suitable spectral space in my mix.
T-Bone is impressive to me in every way. The filter sound is top quality, I immediately noticed how good the sound was compared with my previously favoured tilt EQ. Boz makes mention of special filters that "do not have any of the wonky side effects to your high end". This claim bears out, and I would certainly be interested in more filter and EQ products from Boz Labs.
The GUI is also beautiful and impressive to me. I know a lot of people dislike the Skeumorphic designs, but I think this one works well, and I really enjoy looking at it and using it.
T-bone extends the usefulness of a basic tilt eq by adding a number of features that really help you sculpt and shape your sound. The low and high pass filters are a great addition, and allow me to dispense with one or more extra plugins from my chain. Having the filters and tilt all in one plugin really speeds up my workflow.
The 'Harsh' and 'Boom' controls are great; if you push the treble up, and it's pushed too much into the high treble, you can use the harsh control to smooth the top off. Boom can be used similarly to keep the low end under control.
There's mid/side/stereo options (useful) and mix control (useful for parallel processing) and an analog button, which imparts subtle saturation.
CPU seems very low (I haven't actually measured; I generally only look at my CPU hit if something seems to be using it excessively), I use these all over my projects, and my DAW and I don't notice any strain.
All in all, an incredibly well designed and useful plugin that I use all the time. I don't usually give a 10 score, but until I find something better, I believe T-Bone is the best at what it does.