I've never lived there myself, but I went to school at a nearby community college so I got to know a lot of people who were from there and my understanding is that it is about average. So not as bad as Oakland, but not as safe as, say Danville. It is fairly small, and kind of out of the way from everything--but if you don't mind that you should be okay.
I hear the local high school is not very good either, so that might be a consideration if you have kids. If it is feasible for you, you might try Livermore to the west, which I think is a little better. Good luck.