Unity was introduced with the recently released Ubuntu 10.10 as a user interface for netbooks. Now, however, Shuttleworth has announced that Unity will become the default user interface for desktop users as well, hopefully in the next release (11.04). He claims that users love it, OEMs love it, and it will, uh, unify both netbook and desktop.
With Unity being a netbook environment, a lot of work needs to be done on tailoring it to the desktop, as well. "A lot of work to do around windows management", as Shuttleworth noted, calling it the "most significant change ever" and acknowledging it will be a "risky step".
That's only half the story, though. The direction GNOME has taken as of late did not sit well with Ubuntu. For instance, Ubuntu is not happy with the Mutter window manager, which, according to Shuttleworth, could not deliver acceptable performance (huh, a major Free desktop environment writing a window manager that doesn't deliver performance-wise? Sounds familiar). For Unity, Ubuntu uses Compiz, which already has a proven track record.
Another problem is GNOME's dismissal of Zeitgeist, something Ubuntu would love to have. "Zeitgeist is a sophisticated framework that tracks and correlates relationships between the user's activities so that it can supply applications with contextually relevant information to present to users," Ars Technica details, "Zeitgeist was once considered to be a key part of the roadmap for GNOME 3, but was rejected by the upstream community due to cultural differences in its development model. Shuttleworth says that GNOME would benefit from greater receptiveness to outside innovation and is disappointed that the Zeitgeist project isn't being embraced by the upstream community."
There's more, though, as Shuttleworth told Ars. The design goals, mostly set by other, less-desktop focussed distributions, for GNOME Shell are fundamentally different from Ubuntu's. Shuttleworth cites GNOME's rejection of the global menubar as an example of these differences.
What will this mean for GNOME? According to Jono Bacon, Ubuntu's community manager, Ubuntu remains a GNOME distribution. "There is going to be some questions about this decision in relation to GNOME," he notes, "I want to make something crystal clear: Ubuntu is a GNOME distribution, we ship the GNOME stack, we will continue to ship GNOME apps, and we optimize Ubuntu for GNOME. The only difference is that Unity is a different shell for GNOME, but we continue to support the latest GNOME Shell development work in the Ubuntu archives."
All this was bound to happen. I haven't been able to test Unity yet, but with Ubuntu being pretty much the only home desktop-focussed distribution, it makes sense that GNOME's goals, mandated by the majority (i.e., corporate and server-oriented distributions) would eventually diverge from Ubuntu's.
I am afraid, though, that this will mean that the next Ubuntu release will be one heck of a buggy mess. Clairvoyance? No - experience.