There's a long thread on the Ayatana mailing list about the upper-left Ubuntu button in the upcoming Ubuntu 11.04. Currently, this button will open Dash. But there are also two shortcuts in the launcher which trigger Dash (Applications / Files Places) which make the Ubuntu button redundant - this lead to some new ideas for the upper-left Ubuntu button behavior.
One very interesting idea was posted by Marc Lajoie and he calls it "two-sided dock". Here's how it's supposed to work in Marc Lajoie own words: