Not bad.
If i were you, thing:
1. Remove footer background (that white/grey line above black footer)
2. Align widget advert in center (with div tag)
3. Change color of widget h3 title (maybe gray to white fadding)
4. Change color of footer to fade from grey to white (opposite of top_bar), you have great combined color sample (yellow, blue, grey), don’t mess it with black 😉
5. Play with other colors in main menu… why is everyone avoiding to style menus, I seen dozens of graphene based sites with menus on default 🙂
Nevertheless, pretty good site!