Yes, it can tell you if you meet requirements or not.
No, it does not take into account every single specific detail about your system such as your power supply, RAM speeds, etc.
It is very unreliable though, at least for me. It says I fail even running Crysis 2 on minimum, when in fact I can run it on maximum with at least 55fps.
It says I can only run the first Crysis on Minimum and that I'll have trouble, when in fact I can run it on max with lifesis mod with at least 35fps, extremely playable.
Anyway, FrozenEye, it should be playable on minimum settings. You do only scrape by, as it requests minimum 2GHz dual core and a GeForce 8000 series.