This is a brave release from the team at Canonical. After several years making small enhancements to the Gnome desktop, like the unified messaging/logout menu and the onscreen notification system, it's going the full distance with Ubuntu 11.04.
It's replacing the desktop with a product of its own creation, Unity, which started life on the back of the netbook Ubuntu version from a few years ago, a version that's now rolled into the main release.
Unity replaces the metaphor of a desktop with a full-screen app launcher, file viewer and task manager.
The unified messaging and system controls stay at the top of the screen, but everything else is new. You can switch between common folders and the entire file system using quick links, but here's the rub.
Unlike other versions of Ubuntu, Unity requires graphical hardware acceleration. It doesn't need to be much, but it needs to be more than the stock VESA driver your system may default to if it can't install a native driver. In such cases, it looks like you'll be dropped to the Qt-based 2D version of Unity, which is functionally identical but lacks the eye candy.
A more profound problem is that Unity is very similar in concept to Gnome's shiny new Shell. Like Unity, the Gnome Shell replaces the desktop with a full-screen file and application management interface.
However, thanks to the politics of open source, the projects are fully independent. This means that while all other distributions forge ahead with Gnome Shell, Ubuntu has split itself from mainstream Linux distribution. While that won't affect the uptake of Ubuntu 11.04, it may affect its influence by the time Windows 8 is released.
Add to this the community furore surrounding Canonical's switching of affiliate payments in its new music player, Banshee, and it seems likely that the distribution has a lot of patching-up to do if it's to maintain its momentum.
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