I've waited with baited breath for this title for years...especially the last year...and it has proved worth the wait.
For neophytes, prepare for some frustrating problem solving. Try everything to include the improbable. For experienced gamers, some head scratchers are present. I view this as a good thing. The atmosphere of the original is still present, you have no idea what to do and figure out everything on the fly.
The best thing about Half-Life 2 is that there are ZERO cut scenes to bypass through and you can interact while information is being passed. Oh and the graphics are simply AMAZING. I'm talking interactive movie amazing. The world IS Morrowind'ish interactive but, NOT Morrowind'ish open. The plot line is linear but it's appears as a broad line. Without this linear play the story simply could not develop. This is like playing the lead of a movie. Not simply, lock, load, fire repeat.
However, just like Half-life unless you are running a BIG $$$$ box you will suffer some dropped frames, chop and stutter. During a multi character battle it was like a Matrix slow motion battle. (2.4 GHz, 128meg 8xAGP NVIDIA, 3/4 gig of 3200, SATA drives) I expect to fully enjoy Half-Life 2 in about 2 years when I can afford the Direct X 9 card with 256 megs and a yet to be developed 5 GHz processor.
Kudo's to Valve for pushing the envelope in gaming. Jeers for dropping support for original multi-player.