It depends really. I'll be in the market for a 24" monitor once I upgrade my computer and my current 22" monitor will obviously look different. What I'm going to probably do is buy a stand for the 22" so I can rotate it and put it in portrait mode. That'll most likely be the one I use for web browsing and reading, and it will certainly help when following tutorials since I'm starting to do more development stuff.

I did have dual monitors at one point, but one monitor died on me. It was amazing when I had it though.