McAfee is upset with Microsoft too, it seems. Following Symantec's recent complaints, McAfee has gone a step further and taken out a full-page newspaper ad slamming Microsoft for their kernel locking. The ad, featured in the Financial Times, tries to persuade viewers that MS is hindering security efforts by other companies. They also claim that locking the kernel makes Vista less secure, rather than more secure:

"Microsoft is being completely unrealistic if, by locking security companies out of the kernel, it thinks hackers won't crack Vista's kernel. In fact, they already have."
Interestingly enough, some vendors are able to produce AV for Vista. The article hints at a preferential treatment for some vendors.