this is better than a lot of microsoft plans, and i'll tell you why:
competition.
i still uphold the cathedral/bazaar model, but i also think that if microsoft and others are providing competing products that are cross platform, it will no longer be a case of "*ix + apache versus ms windows 2003 server", because now, you can choose your server's system, independently of the software running on it. This does drive development.
The down side is of course that microsoft knows they cannot win this battle (cathedral & bazaar model again) and so they will probably use their usual tactics of using a huge advertising/propaganda campaign to attempt to wipe out the competition using marketing rather than any real performance, security, stability or even price comparisons, and once they have done this they can set their own agenda regarding development schedules, bugfix releases and forced upgrades.
we shall see....