I don't know how much desk space you have, but I found that working with 2 separate, smaller screens, seems to work very well. I have each configured as a separate "desktop" and some apps start automatically in one, some in the other. I can also shift stuff from window to window of course. Mine are only 16" each because that's the max I could cram onto my desk, but if you have more room, you could go for 2x 17" or even 2x 19".
It's not great if you plan to watch high-def films on your PC screen, but if all you use your machine for is work I recommend at least considering the 2-screen option over a single large screen - and I'd also recommend getting square monitors not widescreen ones if you don't plan on watching films much.
NOTE: you need a video card with 2 outputs and the ability to drive 2 independent screens to configure a system like the above. Not all cards can, although it's quite a standard feature these days I believe.
