I have 2 Dell 24 inchers side by side with blazing fast Ivy Bridge rig that most gamers would envy (I'm not a gamer though, I just like a V12 under the hood). I think this is the most optimal set up for a programmer. With 2 x 27 inch there would be a little bit too much head turning, same goes for 3 any size displays. In my opinion 2 displays is a must for a web developer, since there's always a browser on one display and a code editor on the other.