Scoble has thrown down the gauntlet, and wants to set up The Great OS Debate between Vista and OS X. It's make a hell of a podcast, but I'm not sure what the point is beyond that. What would that kind of "meeting of the minds" accomplish? Would it actually bring people from one camp or the other? Or would it just be a pointless waste of breath and time?
The simple truth of the matter is, the masses use Windows. Sure, there are a small percentage of people that use Macs, but most people use whatever is put in front of them.
Given the option, would people use Macs? Well, Mac hardware is better than Mac software IMO, and I think the recent boost in Mac sales is more due to the fact that you can now dual-boot to Windows than anything else. If Dell offered OS X on their computers as an option, would people choose it? Maybe. But that's the Catch-22 for OS X... the only reason you can tout it as being resistant to attacks is because it's not a big enough target. If they gain too much market share, the attacks will go up.
Having said all that, I'd gladly accept any opportunity to evangelize the Vista platform to people that haven't experienced it yet.