I managed to get Thief Gold running really well with a controller using Steam Big Picture. Even got it working so you can walk if you have the left stick only slightly pushed and run for fully pushed which feels more natural than simply using a button to walk which is also how Deadly Shadows on the Xbox did it (and, well, every console game) but there's something about both 'mouse' look (which translates to the right stick) and movement that doesn't feel 100% comfortable on a controller, which I chalk up more to Thief than Big Picture so I was wondering if there's a mod for true controller support?

Thief: Deadly Shadows can be made to work beautifully on PC so that it feels like it was designed for modern controllers largely thanks to the fact that the game was ported to the original Xbox so it'd be nice if I could get it feeling as good as in that, but I'm almost positive I would've found a controller mod for the old games if there was one. Correct me if I'm wrong.

And, just because there's some petty elitist who feels the need to make people feel stupid for enjoying controllers and wants to snidely inquire as to why anyone would want to use a controller, I want to use it because I want to use it. There. That's as deep as an answer you get. I've played 280 hours (according to Steam) of the game with KB/M if that makes you feel any better.