I know the game is based on the same engine and looks like a great big Fallout 3 mod, but how similar is the system exactly?
Will all the file types be the same and cross-compatible? .nif and .dds? Would people be able to take resources from Fallout 3 mods and use 'em without modification in New Vegas mods?
How about the game files themselves? Still .esm and .esp?


For PC version, of course.

No resources can be taken from Fallout 3 and be used in this game in a mod. However, most of the current resources from FO3 will be in New Vegas.

No mods for Fallout 3 will work for New Vegas. All will have to have some work to be compatible with the new game.

As for dds and such, there are other threads that discuss that, and the answer from the Obsidian Devs is in those threads.

I already brought this up in http://www.gamesas.com/index.php?/topic/1118383-with-fallout-new-vegas-on-the-horizon/

I have found two of the threads that already ask about technical differences between the two games and the editors

http://www.gamesas.com/index.php?/topic/1118804-another-techy-question-to-devs-about-weapon-mod-implementation/

http://www.gamesas.com/index.php?/topic/1116791-techy-question-to-obsidian-devs/

Lets keep these questions to those two threads please. I will close this to reduce clutter.