It's been written and talked about many times: Accepting a counter-offer is usually a recipe for disaster. But too often people are blinded by money or promises. Now I'm sure there are times when it works out, but if there is something that causes you to seriously consider a different job, chances are those issues are not going away. Maybe this is sour grapes from a recent deal that I lost because of a counter-offer (oh yea, it is), but the point remains the same.
If you are consider changing jobs, check this out before you give your notice so that you are prepared. Counter-Offers
Here's another article that spells it out rather well.
Older Article That Still Applys