The cost of training
Businesses considering alternatives to Office of course have to anticipate a steep cost of change. One of the great advantages of Microsoft Office is the number of people who know how to use its applications. In any switch to an alternative, you would likely need to do a good bit of training -- especially of heavy Excel users who tap into the significant and sometimes inherently complex functionality in that product. And don't forget the cost of rewriting all the Excel macros that create the monthly executive dashboard reporting at the company.
The new user interface introduced with Office 2007 is cited by some as creating an opportunity for exploring new applications, since the "ribbon" device used in Office 2007 is so radically different than that of earlier Office versions. An application suite like OpenOffice.org, which features a user interface similar to that used in Office 2003, could require less user training than the new version of Microsoft Office.
There are many third-party options available for training users on Microsoft Office products. But there are significantly fewer options for training employees in the use of other personal productivity suites. Developing application training courses in-house can be an expensive proposition, though such lessons have the advantage of being able to focus on an organization's particular use patterns and standards.
Many organizations don't feel it necessary to provide training to every employee on Microsoft Word and Excel, since so many employees come into their positions with experience in the software. That same level of prior knowledge can't be assumed for other packages -- with minor exceptions. In the legal field, for example, WordPerfect is still commonly used, and experience in its use is expected.
If training can be dealt with, there remain other issues, some of which involve software used by partners, customers, and suppliers.
The cost of compatibility
In a market filled with file formats standardized through committee action, the most commonly used document format is Microsoft Word's DOC file. Yes, there are common file formats, like RTF, and many Office alternatives can open and save to Office file formats. But saving back into those formats to share with Office users can be imperfect. In a business world that relies increasingly on collaboration, these file format issues can become showstoppers.
The problem worsens when the target shifts from word processors to spreadsheets. Many enterprise business intelligence and resource planning packages use Excel as a desktop front end to their data-gathering functions, and they rely heavily both on Excel's format and its VBA macro programming facilities. For example, while Zoho will import Excel spreadsheet files and allow development of VBA-format macros, the user interface is sufficiently different, and the style-import features sufficiently limited, to make it an imperfect "out of the box" substitute for Microsoft Excel at the corporate level.
The cost of support
Support has been a traditional stumbling block for those wanting to try alternatives to the application mainstream, and to some extent, it remains so with the current set of options. Both Zoho and IBM have partner programs in place to develop a channel for providing product support, and both OpenOffice.org and Google Docs have extensive user forums available to provide peer-based support for issues that arise. None of the suites provides the same level of support that corporations have come to expect with Microsoft Office, but they all have support mechanisms in place.