In my experience, it very rarely works.
I have had ample opportunity the last couple years out here sight fishing over untouched, rather aggressive steelhead. Most of the time they don't even react to a twitched jig at all (winter runs that is). The only steelies I have picked up on them are summer runs, some days it can be money, other days not at all.
Swinging jigs... that works for both summer/winters. For whatever reason the twitching doesn't seem to very well (even though bouncing under a float they are money?). I think it has something to do simply with how fast they are moving and how much action you need to put on them to keep them off bottom. The good thing about jigs is they are easy to switch to if spoon fishing (with a spinning reel). Sometimes I'll leave a bobber stop on my line, and if I want to jig fish, throw on a small float and a jig under it and fish pockets from downstream - works very well!
That being said.. I don't use jigs much - I'd rather fly fish if I'm going to be using a "big heavy fly" anyway.