I have tried a handful of commercially made rubs and have tried a few from the books (Myron's, Gibson, Wicked Good BBQ, etc) ... and found a few I do like. However I still make my own for the special cooks.
I grow a lot of my own spices and hot peppers so I am pretty good with consistency and tweaking to get the flavor I want.
With that said though - commercial mixes are awesome (not all) but a few that I like. They save time and allow me to conserve my personal rubs for events I want them for.
Pork Pulling Plowboys
Slappy Your Daddy (chicken)
and a few others...