Q3A and TA just make me sad. I cut my teeth in 3D gaming with Quake 2 (first on a Riva 128, then on Voodoo 2s), and really loved those marathon sessions of Lithium and Action Quake 2.
Q3A's whole goofy sci-fi aesthetic totally turns me off, the guns are really, er, fictional-looking compared to Q2, the sound engine is VERY marginal (especially the horrid "dink-dink-dink" noise when you hit an opponent), the jump pads are silly, and the gameplay just has no punch overall. The graphics are pretty in 32-bit, but otherwise UT has it all over Q3A, and even UT is nowhere near as fun to me as Counter-Strike and some of the other variants of Half-Life.
I had about an hour of decent gameplay out of the TA demo; time to uninstall now.