I have ranted before about my feelings on a dark theme for Ubuntu. Its not so much that I dislike the dark colors, but they should be mixed in with lighter colors to give a good balance. Mark Shuttleworth has recently been informing us about the direction he wants to take Ubuntu. I stumbled upon this mock up theme which really shows that there is hope for Ubuntu. You can use the light and the dark together to make a very attractive theme. It does have a bit of a mac feel to it but it definitely maintains its Linux integrity. I do think some of the programs in the mock up are a little far fetched as support for a few of the programs are doubtful, but there are plenty of great programs for linux to serve the same purpose.