The problem i had with Photoshop and Illustrator (and lately with fireworks) for the web is that they always mess with the points and sizes. I can't produce a 1-pixel exact image.
Whenever I make a header shape of 100,10 in 50,5 I end with a shape with 101x11 or 99x10; I think is because Photoshop and Illustrator are meant for printed material so 1 pixel is not big enough for them to make a difference but for the web and CG 1 pixel is big enough to make things looks awkward (like gaps between shapes).
