IMHO the rational that piracy is the reason people don't switch is almost completely wrong.
The vast majority of people do not pirate Windows. Why would they? As far as they are concerned Windows comes "free" with every system purchase.
The only Windows pirates are people who build their own white-boxes and that is a tiny minority.
Microsoft has a massive advantage, not because of piracy, but because of their distribution channel (Dell, HP, etc.).
Now if every PC did not come with an OS and you had to make a decision between going to Office Depot and buying Vista (or pirating it), or downloading and installing a free Linux OS, _then_ you would see some uptake of Linux.
That isn't going to happen and therefore, in my opinion, Linux isn't going to significantly increase market share _ever_.
I know it's a bold statement but it's my opinion.
I'll just clarify by saying "who cares?". I like the fact that Linux is a niche OS.
If there was ever going to be a significant shift in market share it would have happened by now. Instead the only change recently has been a very minor increase in Mac sales driven by the iPod's popularity.
People only make changes if there is a compelling event and I can't foresee any compelling event that would make people choose Linux or Macs over Windows.
Oh sure there will be a few that switch. And there will be some (like Gilbert) that switch from *nix to Windows (sorry I had to take that shot ;) ) but ultimately nothing will change significantly in the short term.
Actually, the biggest "switching" going on right now is people switching from Vista back to XP.
John