Sven Fechner of SimplicityBliss has posted a mod to the OmniFocus theme Bebas Neue theme which was originally created by OmniFocus Themes user, TAT.
I've been using my custom "Gridwriter" theme for quite a while — but the Bebas Neue theme is probably the only theme that I have seen that makes OmniFocus look "modern".
I currently have Sven's modded version of TAT's theme installed, and it looks great. As Sven said in his post, great job to the original designer.