Just passing this along as the buzz about it is getting a bit overwhelming — which means you should take this as a critical alert.
According to AlienVault Labs (see: New Internet Explorer zero day being exploited in the wild for full report):
The new vulnerability appears to affect Internet Explorer 7 and 8 and seems to be exploitable at least on Windows XP.
However, other sites are reporting that even Windows Vista and Windows 7, with IE 7, 8, and 9 can’t protect you from this, and are prescribing folks to STOP using Internet Explorer until a fix is available.
See: Critical zero-day bug in Internet Explorer under active attack on ars Technica.