You shouldn't have the steps on the width changes exactly line up, it makes the "jaggy" edges more visible. Try making them off by at least one pixel, maybe two. Something like this:
http://img.photobucket.com/albums/v226/ ... ed-3-2.png[/IMG]
You can also try varying the outline color to reduce the appearance of the jaggy edges. Darker colors kinda feel like they're farther inwards than lighter colors even when on the same line, at least, that's my experience.
Also, I honestly didn't see the shading on the lower outer frame until I enlarged it, I think you need a little more contrast.
And that's about it from this amature. Hope it helps. Good start.