Ya.. Wine is a Linux native implimentation of the Win32 API. There is no emulation going on at all. Or at least not in the technical sense. All your stuff pretty much runs directly in Linux, but instead of using Gnome or KDE libraries, it's using wine stuff.
Oh, and indeed Wine is faster and better at Windows then Windows is... except when it comes to running and installing Windows programs. 😛
Certainly ABI compatability with Windows is a big goal with Wine, but it's unacheivable. Windows is to big, to secret (with docs that are often misleading or even outright lies about how certain things work), to complex to ever acheive compatability without direct access to the source code. Which wine folks won't touch with a 100 mile long pole, unless MS says it's ok (which they won't).
The more important thing IMO is Winelib, which allows developers to easily port their own applications not only to Linux, but also to other non-x86 platforms (using Linux or other Wine-supported platform, of course as the base). There are usually minimal changes a developer has to do, and then linux compatability is only a recompile away.
Another thing to note is that Wine is often faster then GNU/Linux itself. Benchmarks of Firefox running in Wine tend to be faster then Firefox directly in GNU/Linux. There are certain aspects to items like the GCC compiler, dealing with poling text files (as opposed to using the windows registry), glibc and things like that that make Linux sometimes slower with highly interactive programs/desktop apps. Customization usually can overcome these limitations pretty easily though.
