The magic of Half Life 2's design is that you very quickly forget that you're actually playing a game. The design is linear and yet set up in a way that makes you feel like you're in total control (and thanks to the physics engine, you do have quite a bit more control than you'd expect).

Even shit that made Trespasser suck, like stacking crates, is somehow integrated into the game in innovative and fresh ways. Valve seriously scored a homerun in the design, but man..I'm bummed about the demo. I had hoped that they'd do something similar to Half Life: Uplink where the demo was an extension/companion to the original game. Instead they released a multi-level spoiler for the full game, which is sadly what most companies do.

If you nabbed Half Life 2 Silver, you'd be able to install Half Life along with pretty much all of the mods available for it, ranging from short and sweet ones like Uplink and Poke646 to long ass epics like They Hunger, Todesangst I and II, and Heart of Evil (Which I need to play, damnit). Plus Todesangst I and II are being ported to Half Life 2 by the original author (who's also updating them to take advantage of the Source engine). UnF indeed.

Finally, you simply need to play BrainBread and Sven Co Op with me.