Currently, I use TAC in both 5.56 and 7.62, although I only have a load worked out for 175gr Sierras in 7.62. It's a good performer in my estimation, and I like the powder because of its:
Relative temperature stability (compared to 3031 and other powders I used when I lived out west)
Ease of metering
Also, it seems to be a fairly clean burning powder, although I don't shoot enough to compare it to much.
It's a tradeoff for me, to a degree, where I'm looking for a powder which can fit many bills and allows me to mass-produce blasting ammo as well as fine tune a precision load.
FWIW, a few the guys I spoke with out in UT who shot service rifle use TAC exclusively now.