And just a few minutes ago, I completed it :-) (had started with my old saved game, which was almost at the end). All I can say is that the game is really stunning. If you like FPSs, this is The One.
There is a lot of variety in the game, as opposed to Doom 3, which I find quite repetitive. Each chapter has its own style and suits the story well. There are also multiple weapons and, as you know, the physics are really well done.
Now, it's time to play it again at a higher difficulty level. I think I'll wait until I renew my video card, though. And also, time to play Half-Life: Source, no matter I've already finished the first game three times :-)