Industry giant IBM produced a survey of enterprise Open Source and Linux deployment. Some key findings from the report are:

• Adoption of Linux is almost ubiquitous within the enterprises covered in the survey. Eighty-five percent, in fact, report that they are using Linux on their servers.
• More than seven out of ten respondents, 71%, expect their deployments of enterprise applications on Linux to increase. Even more, 77%, expect to be increasing their deployments of other types of open source software.
• More than 60% of the smallest companies (100 employees or fewer) now run open source email and messaging solutions,
• The survey finds that 83% plan to implement new workloads on Linux during the next 12 months. By comparison, only 23% expect to deploy new applications or functions on Windows...
• 51% of respondents expect to migrate applications from Windows onto Linux.

The report can be downloaded from here: ftp://ftp.software.ibm.com/linux/pdfs/Linux_Research_study-200610_v2.pdf

A very recent report by Forrester Research and Unisys has confirmed and expanded on the findings in the IBM report. Quoting from the executive summary: "The survey shows that, while cost savings was the most typical benefit desired, there are other economic and technology benefits as well, including improving overall efficiency of IT, quality of products and processes, time-to-market, greater innovation, increased competition among service offerings, and more efficient use of resources across the industry...."

The report is available for download from here: Forrester_research-open_source_buying_behaviors.pdf.