Anyway, to the point. The main changes are:
- Complete support for Vista: both as a host and virtualized system
- Improved performance, as it uses the Virtual Server 2005 R2 codebase
- Support for 64 bits host systems
- Support for something-PXE (who knows )
- Support for the virtualization technologies developed by AMD and Intel (ya know, the new instructions built into the Athlon 64+ X2 and the Core 2 Duo)
Vista support address one of my main complains about these SO: the possible lack of compatibility with old applications. Although it seems that I still need DOSBox to run LucasArts games, newer games like MDK or Silver will probably run wonderfully with Virtual PC 2007. Great!
You can find more information about it here
As a bonus, on the same site, I found some other news about what it seems like a fairly new virtualization solution, VirtualBox. This one seems more complete than Virtual PC, as it can run a handful of SOs, including Windows, Linux, and several other minor SO, like Solaris or FreeBSD. Best of all, it's open source, so everyone can benefit on it. Don't know how well it fares, though.