You guys do realise that no matter how good Leopard is, no matter how crappy Vista is, the vast, overwhelming majority of PC users are NOT going to switch. They are totally accepting of viruses, crashes, instability and the way Windows works and consider Apple and the Mac expensive, different and scary.
The only way Apple is going to bring over switchers is to not only provide compelling products but to ADVERTISE heavily all aspects of the OS. Show it running Office, show it running a million and one different apps.
People won't give a flying rat's arse about the next iteration of OS X because the new Windows is what they will buy because it's what they have always bought. If they were really made aware of the Mac platform, and I mean really aware - massive advertising blitz of professional grade advertising. The iPod commercials have been wonderful but the Mac commercials to date have been woeful. Sure we laugh at them and remember a few they did nothing to stop the impression about the PC using community that the Mac is a sideshow to the Windows main event. They were kooky, oddball and short-running - exactly what the vast majority of the community thinks the Mac to be. Problem is Apple run the risk of alienating Microsoft and losing Office:mac which would be disastrous for the Mac and Apple as a company. Microsoft have no problem ignoring us if they can, sure they'd lose some money but in honesty I think Gates/Ballmer wouldn't really care - they might just take a short break from their money fight.
So yes, Leopard is going to have to be a ground-breaking version of OS X but more importantly, Joe Bloggs in the store is going to have know about it as a worthy alternative to getting a new Windows PC. Cause at the moment he knows absolutely nothing about the Mac.