I don't mean to derail the thread, but how would the size of text compare between 1920x1200 at 17'' to 2560x1600 at 30''?
I'd think it is just a matter of comparing the pixel pitch, but I'm not sure.
As far as on-topic goes, I'd say if you could find 2560x1600 at 27'' go for it, but if you are going for 1920x1200 just get a 24'', because stretching the resolution to fill more area will just make your image less sharp. As far as 24'' vs 30'', id say that depends more on how much space you have. If you have the space to sit far enough away to actually use a 30'', its likely a better idea than a 24'', but if you'll be sitting too close a bigger monitor may be a downside. Personally, I sit about 18 inches from my 17'' laptop screen, so a 30'' would be a bad idea for me. Thats probably more a matter of personal taste though.