I saw this, but I didn't see why this would be any better than WINE so I didn't bother getting it. Okay, a quick search leads me to this:
http://www.codeweavers.com/products/differences/ (at bottom) which supports my belief that it is the same as free WINE, so no, you and I didn't miss anything.
It's WINE with a crap-load of non-WINE patches that let some programs run smoother. It's also much simpler to install / remove / configure Windows software from a Linux GUI, and keeps all the bottles of your programs seperate (so you can run IE 5.5 and IE 6 simultaneously on Linux without them interfering with each other or needing two specific installs of WINE, the configs etc.).
I bought 4.2 because it was MUCH better at running Word 2000 when I bought it than WINE was, despite being from the same original codebase (Codeweavers staff send their patches to WINE eventually where they get critiqued, ignored, ridiculed, included etc.). It was also *guaranteed* to support certain programs, which was why I bought it at the time.
From the one-day trial of 7.1 that I've just done, this is still true - it does a better job at running the Office 2000 install I have on my laptop than even CVS WINE does -I have a 600MHz laptop and the difference is substantial. You might not notice on a dual-core 3GHz but the speed improvements are well worth it to me. It also needs zero "complex" installation such as command-lines, editing .winecfg's etc. (although that's never scared me). The bottles are worth it alone, to eliminate DLL Hell and also so that you can test lots of Windows software without having to wipe out /home/User/.wine each time something blows up. It integrates better into my KDE 3.5 install and actually makes the programs look more Linux-native, including theming and skinning, than Wine does (minor thing, I know).
I actually intend to keep Crossover Office 4.2 (that I bought), Pro 7.1 (this download) and WINE on my machine all at the same time. I don't want my Word crashing while I'm in the middle of editing a 500-page document with thousands of comments and advanced fieldcodes, which I've had happen even on recent WINE. However, for everything else, I use WINE first.