1. I reworked the graphic. Think the edges are better now, but not yet perfect. I'm still learning
2. I agree. They look better at the higher resolution. The banner ad drives the width.
3. I also have versions of this header graphic in 1280 and 1024 widths. Premium members can select between the 800 one, the other two sizes, and several other styles. I had to go with the 800 for the default because when I polled members too many of them still use that resolution and cannot be safely ignored.
The pictures you see are many of my members. They get a kick out of seeing themselves in the logo, and having them in the logo helps show who we really are. I had fun making it. It started out as a fireworks tutorial from sitepoint
Amy