Time for me to chime in with my experience with my Macs 
I made the "switch" almost 2 years ago now.
With my first MacBook, OS X would crash randomly while doing random things. It didn't matter what I was doing, OS X would just crash. XP nor Vista would crash (Boot Camp), but OS X would.
Finally the plastics started to discolor and come apart and the optical drive couldn't properly burn DVDs. So out it went for repair. It came back with a new case that was scratched so bad it looked like it was 10 years old and the DVD writer was untouched. So back out for repair it went. It came back with the DVD writer no longer able to read or write discs and, again, a newly scratched case.
So Apple replaced it.
After a few months the second MacBook's case started to separate and the battery started to warp. Three trips for repair later (scratched up every time) it was finally fixed.
Then fast forward to about 2 months ago. The casing had started to crack in multiple areas, as was common with the plastic MacBooks. So, again, it went out for repair multiple times. This time it came back with a scratched up case that was warped and discs couldn't be properly inserted. The final time it came back the case was perfect BUT the screen had been replaced with a defective one. There were blue spots everywhere on the screen. That system also liked to randomly crash in OS X but not Windows.
So Apple swapped it out, finally, with the new $1299 aluminum unit. So far its been great. Hasn't crashed, it runs and looks great, and the screen is proper.
But I do find myself spending more time in Windows on this system than OS X because Windows is just a far more capable OS. The only way I can see people being truly happy with only OS X after the "honeymoon period" is over is if they don't use their computer for anything other than basic browsing, emailing, or syncing their iPods. If they've been a life long Windows user than they know what they're missing out on as far as software selection and hardware capabilities, so OS X is just too limited.
I made the "switch" almost 2 years ago now.
With my first MacBook, OS X would crash randomly while doing random things. It didn't matter what I was doing, OS X would just crash. XP nor Vista would crash (Boot Camp), but OS X would.
Finally the plastics started to discolor and come apart and the optical drive couldn't properly burn DVDs. So out it went for repair. It came back with a new case that was scratched so bad it looked like it was 10 years old and the DVD writer was untouched. So back out for repair it went. It came back with the DVD writer no longer able to read or write discs and, again, a newly scratched case.
So Apple replaced it.
After a few months the second MacBook's case started to separate and the battery started to warp. Three trips for repair later (scratched up every time) it was finally fixed.
Then fast forward to about 2 months ago. The casing had started to crack in multiple areas, as was common with the plastic MacBooks. So, again, it went out for repair multiple times. This time it came back with a scratched up case that was warped and discs couldn't be properly inserted. The final time it came back the case was perfect BUT the screen had been replaced with a defective one. There were blue spots everywhere on the screen. That system also liked to randomly crash in OS X but not Windows.
So Apple swapped it out, finally, with the new $1299 aluminum unit. So far its been great. Hasn't crashed, it runs and looks great, and the screen is proper.
But I do find myself spending more time in Windows on this system than OS X because Windows is just a far more capable OS. The only way I can see people being truly happy with only OS X after the "honeymoon period" is over is if they don't use their computer for anything other than basic browsing, emailing, or syncing their iPods. If they've been a life long Windows user than they know what they're missing out on as far as software selection and hardware capabilities, so OS X is just too limited.
