At 19", I accept nothing smaller than 1600x1200 @85hz. Any lower resolution and I'm totally pissed (except for games) and any refresh rate and my eyes hurt. On a 17", I will do 12x10 and at 21", I will do 19x14. Space is quite essential for desktop users, if you are going to have that much desktop space, might as well use as much as you can.
vash