You know Microsoft is taking Apple quite seriously when it starts a dual-pronged attack at the time Apple is releasing Tiger.
All the Longhorn hype is using the old vaporware tactic. This keeps people from buying a competitor's product based on the expectation of great things to come from the vaporware company, although the competitor has it, and has it now. It's an old, sad tactic.
Second, the Windows XP ads coming out, trying to drown-out hype around Tiger and keep people with XP just a little longer until they can finally release Longhorn and maybe catch up to Tiger (and by then Apple will be about to release their next big cat).
Security is pretty solid on the Mac. Even if you're logged in as the administrator, you have to retype the administrator password for anything that modifies core services, making it very difficult to accidentally install a virus that can blow up your system. OSX also gives a notification the first time a program runs with an option to refuse permission (in case a virus sneaks through and tries to auto-run). I guess not allowing Internet Explorer to firebomb your core services without permission is an improvement, but it's still a butt-ugly operating system.