The way I see it, especially with all this Quake nostalgia the past few days, is that paying extra for the CE (I'm on dialup so Steam is not an option) is my insurance against a possibly not-all-encompassing experience if HL2 doesn't live up to it all.
As much as I've railed against Valve's BS the past year (my first HL2 preorder is now over a year old) I have to admit - this game gets me excited. The potential of everyone in the old community back and playing a few kickass titles, you know, that kind of synergy (like walking into a LAN party and seeing everyone in the same game) - I really haven't felt that since QuakeWorld. UT2004 came close, but between HL2 and TRIBES, I think we'll feel it again. There's just something about one title being so fun, so fast-paced, so inventive and fresh that it drives you to play it all the time. Something that keeps you engrossed with what feels like endless replayability, with weekends filled with laughs and fun even over the same maps. (Thinking Quake, DII, etc.)
And again, if it doesn't pan out that way, I'll pay the extra $20 for a good old HL remake. That will definitely
keep me interested, especially if Sven does a retro-coop patch for that in addition to his HL2 mod.