Although many people seem to like what ValvE did with HL2 to make it run decently (and it's even worse in CSS) I find it objectionable that they did not provide many options to users to modify that behavior.
I am specifically referring to how HL2 handles shadows and dynamic lightsources. I know that Source is capable of many if not all of the gimmics that FEAR is showing off, but they've optimized the engine such that it is running very well on mediocre hardware. The price is too high though, apparently the optimizations they did are not easily configurable so as a high end user I have no real control over that. For example when playing CSS I'm not seeing my own shadow!! My opponents can see it, so I can't really see where my shadow is giving away my position. Very annoying. FEAR has that covered nicely and I am sure that you can do it in Source, they just chose not to use a player model, and not to render the shadow, for performance reasons.
And then when they find the time to put in new features, they put in HDR (which is easily configurable) instead of proper shadow handling. O well, maybe I'm just picky.