I'm getting the boxed version (special edition) and I'll probably be getting a Steam 'subscription' for $10 per month. Reason being, I like Valve, I trust Valve, and I enjoy the games they make. I like their single player games, I play their multiplayer games... I've played various HL mods for nearly five years now, longer than five years if you count the fact that the Team Fortress guys went to work at Valve.
I'm a Valve fanboy, I admit. Steam has never broken for me. Their games have never failed me. They have given me 5 years of fun for a single purchase of $45 dollars, by constantly updating and improving their game so it remains playable and popular.
This is my way of paying them back... buying the SE and the subscription. I trust them to continue to make me happy in the future as well.
Ancient