After 15 years' development of Wine, we've been through many test and beta versions. Finally, a stable Wine is available to all the users.
Wine is an open source implementation of the Windows application programming interface (API) on top of X, OpenGL and Unix that allows Windows applications to run on other operating systems, including Linux and Mac OS, without the need to run Windows as well.
Of course, open source is free for any users. So they can be build and compiled on your operating system. I used previous Wine beta build on a Linux(Ubuntu 6.*), I had a few troubles:
Fonts was an issue, MS holds the license for all the Windows fonts. If we want to display the same font as windows shows, we have to copy them from a windows pc to the font folder in Wine file structure.
Performance. If you run a basic application should encounter no problem, the one trouble is playing games that requires better graphics. You would expect the performance of the graphic card was reduced. (I played Need for Speed, it was pretty slow while on Windows I can set to higher resolution).
Security. Wine seems to use some crucial .dll(s) in its file structure, you might get some virus that lives on windows, but this should not affect your linux or mac operating system.
My experience was that commercial version(Crossover, developed by CodeWeavers) was decent, however it still had font issue. I was able to run lower versions MS Offic* (i.e. 97, 2000). I encountered a few software crash problem, but the office recover feature worked. (Be careful when you use wine for important tasks, the suggestion is to save your work frequently.) They offered easy setup, however, it lacks of flexibilities comparing to wine.
Well, don't like Wine? but still want to run windows apps on linux or mac? You may try virtual machines. the most well knwon distributor is Vmware as they ship several versions of Vmwares on varies type of operating system. If you are linux users, they ship the Vmware for free( suppose what we call it open source culture). Vmware Fusion provides free 30 trials. It's better than Parallel Desktop, a virtual machine solution for Mac, because the new version offers DirectX 9.0(or higher) support.
If you have time and tried things out, I would like to hear about your experience.. :)