This looks like a great idea. I like the dark screens and have used stylish for dark Gmail and YouTube screens.
One suggestion though: have the logo centred on the page so its position is independent of window size (if not for that, this would be a 5). Have a look at this for an example: http://userstyles.org/styles/1761 (Firefox blue logo about:blank page).
I really like this. Gives the screen some class. One suggestion though: the pale blue background of the read messages takes away from the overall look. Finding a way to change that to a darker silver or even the gray shade of the search box would be a nice finishing touch Thanks pgp
About About:Blank Blue Firefox on Sep 20 2007
About Dark About:Blank and About:NetError with gradient on Sep 20 2007
About Brushed Look For Gmail on Sep 20 2007