This is a major vulnerability that effects all versions of Internet Explorer on all Microsoft Operating Systems versions (including Vista and Windows 2008 server)
This is being taken seriously in the security world, I have received info from a firewall and anti virus provider (I can't name because this is due to work and NDA)http://www.microsoft.com/technet/security/advisory/961051.mspx
Microsoft is currently working on a patch, in the meantime in the very least make certain your antivirus software is up to date.
If you are using Linux, nothing to worry about. The very least you might have a issue if you use IE in WINE or Crossover in Linux. And it would be unlikely a takeover of your system would occur.