I like Web 2.0 looks and nice fonts. The logo should be able to stand on its own (such as a favicon) or with the Drupal Doctor text.
Totally open to colours and I will give plenty of feedback on what I like and don't like. Be as creative as you like.
The logo should be supplied in layered vector format and the name of the font supplied (I don't mind if it is converted to paths as long as I know what it started off as). As for format as long as it is layered vector I don't mind if it is ai, psd or png24.......whatever you prefer working in.