I think a Win XP VM could solve most people's needs, but personally I think it's fantastic that we will have several different solutions such as ReactOS, Wine, and VMs. Eventually you will run into something that won't work on your preferred solution.

It's also nice that they work on different levels. Wine let you run an legacy app on your regular OS, while a VM would give you the entire operating system to fiddle with.

Most people won't be able to legally run XP VMs once the XP activation servers go down.

That's where something like ReactOS fits in. Right now you can legally use a DOS VM running, say, FreeDOS (or an emulator, like DOSBox). There's no freely-available Windows XP equivalent. Sure, sure-- you can run Windows XP illegally w/ a volume license product key (to skirt product activation w/o modifying the product) but that's not a solution that "works" in many cases. It's technically very easy to run a Windows XP VM-- it's very challenging, legally.

If you are running Windows 7, you can run XP legally for free: http://support.microsoft.com/kb/958559