My two cents:
While I loved Neverwinter Nights, keep in mind Doom allowed both user-made levels and user-made enemies etc. So mods are at least as old as Doom, and possibly even older. It depends what you mean by "mods", I guess.
But anyway, there's a huge difference between mods that adds or removes small things to make the game better for you personally, and mods that fixes things that's just plain broken. I'm all for adding or removing things to make the game better, like installing a ducktape-mod in Doom 3 to add a flashlight to your weapon. It simply means it's possible to see in front of you, as it's not all pitch black most of the time. Doom 3 is very much playable without it, but adding it made it a bit better for me. And of course, there's Project Nevada for Fallout 3 and New Vegas. It adds things like visior for your helmets, a grenade hotkey, a better reticule and so on. Nothing game-changing, but it makes the game a lot better.
What I hope for with DOS are mods like that. Most of us have tried the game already, and we all enjoy it a lot. I don't think we'll stop enjoying it when it's out, and certainly not so much that we'll need mods to fix anything. But I wouldn't mind a mod or five to change up the gameplay a bit, or add features the developers haven't added for whatever reason. More spells, more weapons, more classes, more areas... you name it. A good mod can extend the life of the game a whole lot. In fact, many games survive for years mainly thanks to mods. Think Fallout 3/New Vegas, for instance. Both are getting old, but mods are keeping them both alive and well.
