I was a big HL supporter before it came out, spent a decent amount of 1997 in #half-life instead of doing my college apps. Being a teenager I aligned myself with one game and thought competitors would be trash. Much like Tumbler.
The SiN demo shocked me, though. So much fun. It had a few bugs, but I loved writing my name in bullets and loved blowing things on desks up. I also loved finding the way to use the sniper scope with every weapon in multiplayer.
I never bought it, though. HL literally came overnight and made the plot seem outdated. It would be like watching Cobra immediately after Die Hard.