I'm happy to say that you can now buy Visio 2007 online and at stores. This is a huge release for us so it is great to finally be able to have it out there broadly.
If you are looking for more information on what you get in this version, you can find my posts on Visio 2007 by using the "Visio 2007" tag. Office Online's Visio page also has a lot of good information.