If you're talking about working at normal eye distances for a computer, i.e. maybe 30 inches or so (I lean back in my chair), then yeah, I think 30" is getting toward too big. Large panels aren't meant to be viewed close up. Even when you run them at high enough resolution that you don't experience any coarseness (as I would if I sat 30 inches from, say, my 37" Sceptre at 1920 x 1080), I think you're just doing too much panning at that point. I want to be able to "take in" the entire desktop without moving my head, but probably people who are used to multiple monitors don't feel that way.