Needless to say, I'm elated.  Now,

1.  I understand that the single player goes pretty quick - how is the multiplayer?  Does it meet up to prior COD standards?  And if you're really bored - care to share some quick tricks so that I can be ahead of the game on this particular version?

2.  The demo ran fine and looked pretty on my GeForce 7300LE, but would it really be worth it do you think to upgrade?

IMO the singleplayer is the best part of the game. It has the COD feel to it but with improved modeling and effects. The only things I'm not crazy about are how enemies just keep respawning at the same positions until you advance to the correct position. Overall it kicks much butt though.

I've only played the multiplayer about 5 hrs so far but I don't like it very much. To get where I'm coming from, IMO the original Rainbow 6 from the late '90s and the original Ghost Recon game are still the best multiplayer shooters I've played.

Quoted: IMO the singleplayer is the best part of the game. It has the COD feel to it but with improved modeling and effects. The only things I'm not crazy about are how enemies just keep respawning at the same positions until you advance to the correct position. Overall it kicks much butt though.

That's pretty standard through out the COD series, it's a "tripwire" based progression. That being said, COD4 is about the most perfect FPS on the market today, both single-player and  XBox Live.

mp is awesome

It's a phenomenal game!!

Single player is fantastic, haven't even tried multi player yet.

Upgrade for your video card all depends on the rest of your PC - but the nVidia 8800GT's are the current price/performance winner. (I've just finished building a new PC (today!) and it's got dual nVidia 8800GT's in it. I can max out the detail in CoD4 at 1600x1200 res.)