StudioPress has a nice tabbed navigation bar, and a great sidebar with plenty of horizontal space, as well as the ability to split a section of the column into two columns, for link lists and the like.
There are plenty of possibilities for customization, providing you know your way around CSS, or you could just use as-is. One idea would be removing the very large RSS icon and putting a smaller one in the rather empty blue bar along the top.
Comments have alternating backgrounds for easy readability, though I don’t believe there is built-in support for a different style for the post author. That could be remedied with a little bit of CSS and PHP magic though. (There are plenty of tutorials on doing this if you can’t figure it out yourself.)
There’s room in the sidebar for whatever sort of ad format you prefer, large rectangle, skyscraper, 125x125s (either in a single column, as seen on this blog, or in the 2xWhatever formation seen elsewhere).