It's an excellent piece of glass. The AF often seems superfluous on a WA, but when all the other lenses in your kit are AF, it can be frustrating to have one that's not.
Frankly though, for our general purposes we get a lot more use out of a 20mm than the 24, especially with the crop factor in DSLRs. If the price was right I wouldn't hesitate to pick it up, but you should recognize that you might eventually want something wider as well.