Satisfying. So satisfying.
Psi-Ops is a smorgasbord of every goofy psychic power you've ever heard of, and the levels are just excuses for you to plunder your mental toolbox to come up with cool, creative solutions to tactical problems. They give you the Swiss army knife and turn you loose.
The level with the missile silos? I played that same level for two hours straight. I could have finished it in a quarter of that time, but I stuck around because I was having so much fun. The bad guys kept re-spawning, and I kept coming up with new and exciting combinations of pyro-kinesis, telekinesis, brains-popping-out- of-their-skull-kinesis, and a dandy assortment of firearms. I really couldn't get enough of this gameplay, and every situation was worth waiting for a re-spawn just to do it again, differently. There's even stealth, for Pete's sake.
Typically, a developer starts with a laundry list of features and a fat stack of content ideas. As they go, they get hung up on the content ("we gotta have twenty levels") and start cutting features. Psi-Ops is the opposite: they put in every single feature they possibly could, and then let the levels shuffle halfheartedly into existence. But it doesn't matter, because the feature set provides so much gameplay and exploration that the levels are just sandboxes.
Titles like Psi-Ops should be the real future of gaming. The developers' great innovation had little to do with technology; Havok was already standard operating procedure by the time they got their mitts on it. What made Psi-Ops the most entertaining game of 2004 was its design, the real sense of play that comes when someone gives you a sandbox and a sack of toys and says, "Have fun!" When I played Psi-Ops, I did.
That day in Montreal, I saw myself converted from flesh to bits in a matter of minutes, the kind of Tron moment we'll all have someday, so that when our brains pop out of our skulls we can just download them again. But the hours I spent playing Psi-Ops made it clear where game developers should really put their dreams. The game's the thing, and no normal-mapping, HDR-lighting, virtual-reality foofarah is ever going to change that.