Gartner are just a bunch of whores....they'll do a position paper touting anything (or ripping anything) if the money is right. Apple's market share is now up over 6 percent, and dollar to doughnuts, when Vista arrives with all of it's myriad issues, Apple will likely hit 10 percent.
I was at the Gartner conference. They are basically telling their clients to forget upgrading to Vista anytime soon -- er, but keep paying us and we will tell you when.