Some interesting data from the Wall Street Journal regarding Apple's upcoming release of Mac OS X Leopard (see my WinInfo article about this news): 

Leopard will arrive in stores as Mac sales are growing at more than twice the pace of the PC market in general, helping Apple make small, steady market-share gains against its primary rival, Microsoft Corp., in 10 of the 11 most recent quarters.

Apple does a small fraction of the overall PC business, with a 3% share of new shipments globally during the second quarter, up from 2.5% during the same period a year earlier, according to IDC. In the U.S. during the second quarter, Apple had a 5.9% share of new PC shipments, up from 4.8% a year earlier.

Mr. Jobs says even incremental gains are meaningful for the company, with each percentage point in share gain totaling approximately $1 billion in sales.

Within the domestic consumer market, Apple shines even brighter. Through the end of August, Mac sales accounted for 8.3% of the U.S. retail market this year, compared with 5.2% during the same period in 2006, according to NPD Group Inc.

These are interesting figures. It's impossible to deny that Apple, finally, is making inroads, most obviously in the United States of course. That makes sense: Apple's PC products are still essentially luxury items that compete only in the top end of their respective markets. While Apple CEO Steve Jobs speaks of a "tipping point," however, I see more of a plateau effect in the making. Maybe I read this wrong, but it seems like luxury items can only account for a certain percentage of any market. For Apple to gain more past that, they'll have to join the commodity world, which is where the company is now heading with the iPod, incidentally. (Thus the iPhone, which is a way to keep charging repeat customers a premium for high-end products.)