"... infect unprotected Windows users who stray onto maliciously constructed websites
Porn at your own Risk!"
Not just porn. Warez sites tend to be buggy, some newsgroups(age showing), and chat programs can be vectors for the malware.
Opera, Mozilla, Flock (beta), Firefox, and others may not be a bad idea till proprietary Internet Explorer hole (PIEHOLE) gets closed.
Top sends
This type of attack isn't very effective against most people who don't go to such sites. It could be extremely dangerous though, if someone incorporated it into a hack of a legitimate site. I'd asses the danger of this defect to be low risk, but MS should put out a patch promptly to protect their customers.