I agree completely. I work at a huge MS shop as well.
Sasser? Non issue. Attachments aren't let in, virus scanning is up to date, the proxy has content and virus scanning...
In reality the only way Sasser could get through is through laptops, and even then it would only get as far as the least protected machine.
Moving to Mac won't solve their real problem: training, knowledge, management.
Today, again through OSNews, I found this:
Mac OS X vulnerable to one-two combo attack | CNET News.com:
Apple Computer got hit by a double whammy this week when a security researcher publicized a pair of flaws in Mac OS X that when used together could let attackers place a malicious program on a Mac and then run the file.
I have nothing against Apple. I just think that software is complex business. If you have a company out there that is relying on software (from Microsoft, Apple, Open Source or whatever), remember only a few really know how to get it to work right. Beware of the self called wizards!