[dshankar]

It's not just about resolution as some have pointed out. I like to have Terminal, emacs, XCode, Firefox, Preview for any PDFs all open at once.

That's why I prefer 15/17" + external 22/24" - I would never be able to handle the small 13" just by itself.

[forensic]

I generally am using 8 to 10 Spaces desktops at a time, with several of those desktops running multiple windows. With Spaces and Expose I find it good enough on a 13" screen.

Bigger is always nicer, but the tradeoff is that it would be a lot harder to carry my laptop with me. I prioritize mobility.

[dshankar]

I only use 2-3 Spaces (to separate work from chats and distractions). I find it hard to split up "work" into multiple Spaces when I need to look at all of my work at once (ex. need reference docs + code up at the same time).