We're doing a lot on the backend to make the game accessible for everyone.
There is no delay for the PC version of MW2
There's prestige mode
Jason West at the MP event, said that he was dead on, on the matchmaking servers. We've been building a system on the backend called IW.NET.
You are completely reliant on IW.NET. There are no server lists. There are no dedicated servers.
You have private matches where you can customize the game
You cannot put MW2 on a dedicated server.
This is the first time we've ever done something like this and the team has huge plans for what IW.NET develops into.
Customizing your game...you have quite a few options in a private match
You're getting same game (as in Console), plus matchmaking and private match.
Server admin point-of view, NO DEDICATED SERVERS
I've summarized some of my own thoughts from the cast here:

General

IW partnering through Steam is what you will see in the future. Matchmaking is not through Steam, but IW.NET is run in conjunction with Steam.
GSP's will no longer be renting out servers.
No PunkBuster. VAC will be used as an anti cheat.
Retail distribution: Pre-orders will get a disk. Or you could order from Steam.
DLC may now need to be paid for - not confirmed.
Piracy was only a small reason for going to IW.NET - not the whole reason.
Clans:

No more clan servers. Private matches, replace clan servers.
Listen servers will connect to each other.
IW.NET/Steam will replace the community server admin
Competitive Gaming

Competitive gaming has changed as we know it.
It might be possible in the future for IW engineers to load a "competitive" setting on IW.NET, but it is far from a guarantee. It might also never happen.
Modding

Modding the game is now very much in question. Fourzerotwo had no info on modding. However, it appears that there will be no community mods or maps for MW2.
Modding in SpecOps? Unknown.