Slashdot reported a long-term field test by John Halamka, CIO of Harvard Medical School and CareGroup regarding Operating systems in corporate environments on a notebook.
The power of Windows lies in its availability for niche business software, OS X and Ubuntu appeal to the usability and enterprise Linux systems such as Novell and RHEL focus on Windows like usability and are meant to fill the corporate Client/Workstation segment.
Regarding Linux strategies, enterprise solutions should be the first ones to take some market shares from Microsoft in the corporate segment.
Ubuntu is gaining more and more support due to its stable Debian base and its usability. Taking Ubuntu to the corporate sector seems very possibly but this may rely on further strategies of the Canonical Foundation.
One thing regarding Debian: There may be some confusion to people jumping in the Linux sector regarding the Debian policy on non-free software. The fact is Debian is very attached to its roots in the GNU and the ideology of the Free Software Foundation which is a good sign in times where Linux distributors are contracting with Microsoft, the very company that states open source as something evil and a violation of individual intellectual property and tries to stop the growing success of Linux by fear mongering potential users by stating that Linux and Open Source violate several hundred Microsoft patents without delivering a proof.