Q3A is the most responsive, intuitive FPS experience ever created and it is because of the eloquence of the code that comprises it. I'm sorry to pour on the superlatives, but it is true. Over many, many hours of serious deathmatching the game has yet to hang on me once. It is rock solid, and beautifully balanced. I am not referring to the relative power of weaponry and powerups.
Movement syncs smoothly with player actions.
If you slide the mouse sideways, jump, and fire simultaneously, it all happens onscreen seamlessly. There is no perceivable distance between input and result. Consequently the game is completely immersive. You are not struggling with a frustrating gap between what you wanted to do and what actually happened onscreen. You are freed to respond unfettered to the action.