As a designer I am pretty particular about my images, and I have never been happy with the optimization and resulting quality of GD images, gif or jpg. There is no comparison between those images I optimize in Photoshop and those produced by GD.

Maximizing the color settings helps, but does not seem to have an effect on the overall resolution or quality of the image. It seems there must be other mitigating factors in how its "engine" does the work.

I have never tried Image::Magick, but I get the impression from what I have read that it is better. I have also gotten the feeling that Implementing it is difficult it, but I have no experience.

Anyway, you're not alone. My 2¢.