I heard about the source bleed not affecting release, Hsu. What I'm pretty sure it was, was the whole, "We have to rebuild the entire game for Nvidia's cards to work right" problem. They did have a whole two year head start on Doom's developers, though (they said somewhere that they began working on it immediately after Half-Life 1...and that came out in 1998...so I can only assume they started work by 99/00).
I'm not excited about Doom because of its engine, though. What really gets me excited is that it's going to be an immersing experience. After reading the first two Doom books at a young age--which were admittedly mediocre, but still--I often had nightmares that I was that marine, combatting the demons. I have always been a fan of the marriage of the occult and sci-fi and doom is the ultimate expression of that union. Mix it with a healthy dose of action and a nice amount of immersion and you get what is probably guaranteed to be an experience of enjoyment. Few games besides ESF have given me a true sense of immersive enjoyment; even Half-Life didn't, really. The Quakes sure as hell didn't. There was only Doom, and even then, Doom wasn't nearly as impressive in scope of experiences promised as its retelling is supposed to be.
I'm just looking forward to a good fun time with it, is all. Engines aren't as important to me as fun is.