Originally posted by Tevirik:

You know, I think that nobody can absolutely garantee your world won't get broken if you use mods. There are too many variables. Like if you install your mods properly, if you install too many of them or conflicting ones.
What I can say is : I've used mods for hundreds of hours of games and never broke a game; But that's me.

I know that guarantees don't exists :) But you can often find out how well the mods work, by asking the community.. For example, I would not rate Fallout too high, as the mods can kill your save files