It helps with legacy apps but still has a lot of problems. Like the article says it's not an emulator so it won't work with non-x86 processors like the older PowerPC-based Macintosh. There is a project named "Darwine" that combines Wine with QEMU to get it working on those (but with the obvious performance penalties).
With the alpha releases the developers didn't care much about new features breaking it but with a 1.0 release they should be more concerned with regressions now (only time will tell).
Wine-Reviews has reviews and news about various Wine-related projects. There is also a
mailing list.
Installing Windows apps can be difficult but projects like
Wine-Doors and
PlayOnLinux are developing front-ends that automate the installation of popular apps and games. Still there are many apps that don't work correctly or completely but many popular ones are supported. It is getting compatible enough that the developers are concerned that Windows viruses may become a problem.
It doesn't use any Microsoft code so there is no copyright or licensing threats. There may be patent issues but that's no different then any software in the current US patent system.