No Accel when I have begun to play on Quake 2.
Accel when I have begun to play on E+ (low sens+average accel, easy for beginners).
No accel when I have begun to play on DeFRaG (easier to strafe-jump and to aim with accuracy, FOR BEGINNING, in fact).
Accel when I have begun to play on Quake Live (harder at beginning, but really more useful at end).

Playing without accel' is really easier for aiming at beginning, but in fact, adding acceleration properly will be really more powerful (I mean an acceleration you can control, according to your sensitivity).