The reason Windows 7 isn't listed is because it's still just a beta/release candidate and not an official operating system. If they were to list Win 7, they would have to support it.
For that matter Microsoft doesn't even support Windows 7 RC 1 and won't until the RTM (Release To Manufacturers) version is out.
You won't find any software companies officially endorsing using their products under Windows 7 right now. I can't even get technical support for Kaspersky Internet Security for Windows 7, in spite of the fact it's the beta FOR Windows 7.

But ziggie (and I think one or two others) has already posted that it runs fine under Win 7.
Windows 7 is more or less Vista, and I haven't yet found anything that won't run under Windows 7 other than McAfee Internet Suite. Everything that runs under Vista should also run fine under Windows 7. McAfee won't, because an anti-virus is tied in more closely to the shell than a program such as Poser, or most other programs, so it's more dependent on OS build.