Kevin Browne, the head of Microsoft’s Macintosh Business Unit, provided further details to MacUser on the comments he made a few days ago in a Wall Street Journal article (paid subscription required). “We’ve announced that we are already working on the next major releases of our Mac products, but have concerns about the long-term because Apple has not focused on moving the Mac installed base to Mac OS X,” said Browne in an email to MacUser. “We do a tremendous amount of marketing on Mac OS X and I’m proud of the progress we’ve made with the platform since it was introduced last May,” countered Phil Schiller, Apple’s VP of worldwide product marketing, in an eWeek article.