Why is Ubuntu switching to Unity?

This Arstechnica article based around an interview with Mark Shuttleworth (the founder of Ubuntu and Canonical) gives some reasons for going forward with Unity, as opposed to using the GNOME Shell.

The GNOME Shell is the major new component of GNOME 3, that many people are incorrectly referring to as simply 'GNOME 3'. Remember that future Ubuntu versions will still be based on GNOME 3 - the underlying infrastructure, applications, etc will not change - they just won't use the GNOME Shell by default.

• Ubuntu would like to embrace different ideas to other parts of the GNOME family - specific examples mentioned are Mac OS X style global menus, and heavier 'Zeitgeist' integration.
• There are concerns about hardware support with the Mutter technology GNOME Shell uses. Whilst Unity has up to now also used Mutter, Unity has been ported to Compiz, which, through its inclusion in default Ubuntu for over three years, has proved itself to have excellent hardware support.
• Recent Ubuntu design work, such as Application Indicators and NotifyOSD are likely to be incompatible with GNOME Shell, and we want to keep these improvements, not move backwards!
• Other distributions may have different user bases and needs. Ubuntu has a lot of home users, whereas many other distributions have more commercial users in workplaces. Canonical employs a lot of professional design experts and they may feel they can do a better job than, or at least take a different approach to, the existing GNOME Shell.

This article at Arstechnica can maybe shed some light on this.

I also asked Shuttleworth why Canonical is building its own shell rather than customizing the GNOME Shell. He says that Canonical made an effort to participate in the GNOME Shell design process and found that Ubuntu's vision for the future of desktop interfaces was fundamentally different from that of the upstream GNOME Shell developers.

So basically, the Ubuntu Guys think that their vision of how a desktop interface should be is too different from vision that GNOME has with GNOME Shell. So they don't try to adapt GNOME Shell to suit their needs but instead they develop something entirely new, Unity.

GNOME3 (and GNOME Shell) was delayed, and as I understand it the GNOME devs are not receptive to Canonical's design wishes, hence Canonical are pushing on with their own GNOME shell. There's a Slashdot story about it, though how informed some of the commentors are remains to be seen...

Canonical wants to step away from GNOME and those desktop environments to create their own new next-generation desktop, not just using something out of the box, which would be what they would be doing if they used GNOME 2x or GNOME 3 Shell.

I have dualboot and so always compare ubuntu, gnome and win, just the GUI!!!

If you know win7 and then compare it with unity, you will see that there are not may differences. So, I don't think that unity is something entirely new. It is just compiz like before with a panel and a dock, which is the same like win7 taskbar, just with a global menu.

Why? Quicklists = Jumplists both combine starter and tasks (or grouped windows) the grid in unity and gnome 3 is the aero-something in win

the start menu of win7 startmenu can filter recent documents with mouse over the related app. Unity has nothing like this.

the Lenses in Unity are realy different and will have some good features in the future.

gnome3 is realy a entirely new, next generation desktop. Unity just made its way into the present.

Maybe Unity likes to make it easy for windows user to start in the Linux world while gnome3 is too different.