Mark Shuttleworth has recently announced plans to rock the Linux user experience (yes, I know I'm a week late; I've been on vacation and am just now catching up).
I've been an avid Linux user for about a dozen years, first on Red Hat, then Fedora, and lately Ubuntu, and I've had my share of frustrations with the OS, so I'm thrilled to hear about this initiative.
And I have a piece of advice: don't be afraid to cross (and dissolve) boundaries between layers of functionality and give developers the authority to fix problems no matter where they reside, even at the risk of ruffling feathers (as did ZFS with its "damn the software stack, full speed ahead to the desired outcome" approach).
I say this because my small window into the GNOME development process (bugs 482354 and 162726) suggests its developers spend way too much time trying to figure out which of the many layers of functionality in the Linux desktop is responsible for an issue (and thus who is responsible for fixing it).
Mozilla isn't perfect in this regard either, but when it works well, it's because developers take responsibility for making the user experience great no matter what part of the code needs to be touched (like the recent progress being made in bug 248970 by Ehsan Akhgari in collaboration with others on a private browsing mode for Firefox).
If you want to rock the Linux user experience, be willing to rock its boat as well.