Well, I got the dreaded "Please insert correct cd-rom" bug/protection but nothing a no-cd patch can handle. Actually I had to enable my onboard soundchip to read the cd *temporarly* now it seized completely.
But the game is a blast! I play on *realistic* level - very, very challenging. In fact the best AI I experienced in a FPS. They use their senses like eyesight and hearing. They call for help when outgunned, they hide and use cover very effectively. They even try to flank you - with good success I have to admit. Plus, on realistic they have the same damage model as you. So best stay out of gunfights and try to kill em silently with aimed headshots. Some of them got bodyarmour, others have shields. They even use flashlights to find you. Another breed are the mutants - they are straight forward and fierce. You're really screwed without the shotgun. They jump like 10m and one or tow slashes with their claws are enough to take you out.
Another great feature is the freedom of movement. In the outdoor levels you can take whatever path you want - some are easiser, some are harder. You can swim around the islands or rush straight trough in a jeep - or try to avoid all contact by sneaking through the jungle. The indoor levels are more linear but still very atmospheric.
Greatest thing: GFX - absolutely stunning!!! On my Rig (Athlon XP 2.4 OC @ 2.3GHZ, 1024MB RAM, Radeon9700Pro, Audigy2) I can run medium settings smoothly or high settings at a decent framerate with some dropouts during firefights. You've never seen better use of bump-mapping and reflections. The lightning effects are just state of the art and enchance the gameplay. Sourround sound is very nice and gives you a real advantage while sneaking around the corners. All models are high poly and the textures are beautiful. Both outdoor and indoor landscape are so rich in detail that I sometime just stood there and admired the GFX.
Also very well done: physics engine. You can throw up your enemy by running into them with your car, push down barrels a steep pathway to run over a pack of mercs. Shoot up explosives and see bodies and parts of the architectures fly around. Jump down cliffs, fly a glider around the island, etc. ...
All in all the best FPS yet - HL2 has to put up a very good show to top it. The story