In theory, with a sufficently mature WINE, any Windows program can run on any *nix box. This means you only have to create one kind of software to get all the rest, and not just on GNU/Linux, either, but for all of *nix. If another Free solution that a lot of people would like to move to (perhaps GNU/HURD will be one day), but it doesn't have binary compatibility with GNU/Linux, we have to ask for all those programs to be ported all over again.
OTOH, if WINE can run it, all we have to do is port WINE to GNU/HURD and we get the whole bundle.
So my suggestion is that we don't ask for companies to port their program, but rather, we should be asking them to put the programmers, who would have been working on porting the program, to be put to work hacking on WINE. This way, the duplication of effort is minimized.
This isn't perfect, of course. As stated before, in theory a sufficiently mature WINE will run any Windows program. As always, turning theory into practice is very difficult. Some programs have a hard enough time running between versions of Windows, much less an "emulated" version of Windows. Still, the effort to port a single program will be greatly reduced. If a program needs only minor patching to run on WINE, then I think WINE has done it's job.
Still, you will get a slow down with the emulated API layer. Just how much (and if it's actualy slower then Windows) may depend on a lot of factors. Games might suffer the hardest, depending on their features. I wouldn't want to run Unreal Tournament on WINE, although I have no problem running Starcraft and maybe somewhat older shooters like Half-Life. WINE does have facilities available to help in porting the program to a native binary, so games will still benifit, though perhaps not as much.
In all, helping WINE can only help but smooth the translation of those moving to GNU/Linux. Right now, I beleive that it is one of the last places that GNU/Linux needs to take the desktop. Ease of use is almost a non-issue (just look at Mandrake 7.2, which I shamefully admit to installing once), although we still need to be able to buy GNU/Linux boxes off the shelf at CompUSA and Best Buy. However, getting WINE mature may help eliminate these last few gaps.