I've wanted to implement some form of anti aliasing for a while now so I took a break from playing through the recent Humble Indie Bundle and looked into it. There are several different options when it comes to AA in deferred rendering so I've started with what seemed to be the easiest. The method I've used here is the one outlined in GPU Gems: Deferred Shading in Tabula Rasa and I haven't really deviated from that article with regards to AA.
I also took the opportunity to look into applying a post process sharpen to the overall image. The method is known as unsharp masking and it's an effect a lot of digital artists use to spruce up their images. It goes back further actually and I was surprised to learn that the technique was pioneered in conventional photographic darkrooms.
You can see some examples of AA and unsharp masking below. Be sure to view them full screen without any scaling as the difference is hard to spot when the images are down sampled. In some areas the sharpen effect over sharpens fine details and increases the aliasing problem although for the most part the effect is an improvement.
Fullscreen examples (click for larger versions)