When people insist that they must have a particular Windows application, they are usually confusing their love of habit with their actual needs. After all, they are hardly being asked to switch from a graphical interface to a switch-heavy command line tool. They are switching to a functionally equivalent program in which some tools have different names or are accessed from different places, and nothing more. Many layout elements, such as the positioning of menus or copy commands are standardized across operating systems anyway.
Since this situation is improving rapidly, getting Windows apps to run on GNU/Linux seems a misplaced priority. It would make more sense to give native apps the final boosts they need than diverting funds into efforts that work against native apps. Probably, it would be cheaper, too. For such reasons, running Windows apps natively is an interim solution whose time is drawing to a close.
One of the arguments used in defense of such efforts -- for instance on the Wine project's page entitled, "Why Wine is so important" -- is that they make migration easier, since users can continue to use the same applications.
However, this argument overlooks the question: why people should switch platforms to use exactly the same applications? This ability didn't encourage people to switch to OS/2 back in the 1990s, despite settings that made Windows programs run with greater stability than on Windows, and nothing has changed today. If you want to keep running Windows applications, it is less effort to keep using Windows than to go through an operating system installation and learn a new desktop.
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Admittedly, GNU/Linux is generally a more secure environment, but those concerned with security rarely make the decision to migrate to a different operating system. Nor does security trump convenience in most people's decision-making if they are non-technical. Besides, you can get exactly the same advantage by running native applications.
Another common argument is that an emulator or compatibility layer can help GNU/Linux break out of a vicious cycle. The operating system, they argue, lacks market share because it lacks applications; at the same time, it lacks applications because it doesn't have the market share to encourage companies to develop for it.
Aside from the fact that this argument is becoming obsolete, as I already suggested, it is based on at least two fallacies. First, it assumes that, if a GNU/Linux market is created, companies will develop for it. But why should they, if a project like Wine has already done the work for them? If the Windows version runs decently on a free operating system, why would a company waste resources on developing a native version?