Microsoft's latest ploy to thwart malware writers from harming Vista machines has come under much criticism. Most recently, Symantec has complained that the restrictive nature of Vista is counterintuitive. Many “code-related” issues that Symantec has brought up have only been partly resolved, and they believe that Microsoft is intentionally preventing/regulating the security possible on Vista:

"Microsoft is using their dominant position to regulate what security can be provided on their system and how that security is provided," Rowan Trollope, Symantec's vice president for consumer engineering, told TechNewsWorld. "Microsoft has regulated what choices are there: 'You're going to have our stuff no matter what.'"
Of course, being the developer of the OS, it's Microsoft's prerogative to develop the way they want. Despite the proliferation of server and desktops with open kernels, this is the step they are going to take. Is kernel access even required, however? Symantec may be forced to change their software model to work with Vista if Microsoft doesn't relent.