Games that allow modding are, overall, IMO great. It lets you play the game the way you want to play it, not the way some particular dev(s) thought you should play it.
It's also great that companies like Bioware, Obsidian, Bethesda and others have seen fit to include toolkits (or to support community efforts to do so) - they can't lose; first, it increases user satisfaction with the game, extending it's shelf life (which means $) and (b) it makes those of the community more like lyto buy another of their games (which means $).
Yes, Virginia, it really is all about profit. But it doesn't mean we have to lose out: I still enjoy firing up NWN1, KotOR and KotOR2 and trying different mods out. Sometimes I get unlazy enough to mod myself (scripting is a particularly tasty morsel).
So yes, by all means, try the various mods out there and enjoy them. Hint: Save often, make backups.
And remember - if you don't like what a particular mod does, uninstall it (hence the "make backups" hint )