If you are doing enterprise software, a lot of users will have small monitors at low resolution. Or if they are old they will have it at a low res so they can see giant buttons ( I have seen an 800x600 on a 24"ish monitor). I have an old 15" monitor at a low resolution (800 x 600) so i can see what the program will look likes in less than idle conditions every now and then. I know that enterprise users pretty much have to accept what they are given but if you design a winform that doesn't fit into an 800x600 screen, it's not helping anyone.
