From News.com in a broader article on Linux, starting with some OS history:
Windows trounced OS/2 in a furious operating systems battle back when George Bush Sr. was president and Lou Gerstner was still busy at RJR Nabisco trying to sell folks more Velveeta and Tang.
Smartly retiring from a contest it had little chance of winning, IBM left the field to Microsoft, which cemented its desktop dominance and emerged as the most powerful software company in history.
There things stood for over a decade, but–F. Scott Fitzgerald aside–there are second acts. In this rematch with Microsoft, Big Blue has the stronger hand, owing to its very public embrace of Linux three years ago.
IBM is bent on making a commodity out of Intel-based hardware with an operating system derived through the open-source process. Its pitch to corporate Unix customers running Sun Microsystems’ Sparc or other proprietary chips is that Linux on Intel offers virtually the same performance–but at a far lower hardware price. Once they bite, that then opens the door for IBM to rake in the money selling middleware and services.
If IBM pulls it off, Microsoft risks getting cut out of a lot of corporate business.