Okay, so there weren't a whole lot of drivers (only three), and they weren't ones most people would be interested in (there won't be better support for hardware such as sound cards or wireless chips because of them), but it's another interesting move from Microsoft nonetheless. The drivers were also released under the GPLv2 license.
At first-glance, it brings one to wonder what Microsoft's angle is. Everybody, after all, has an angle. As it turns out, these three drivers are made specifically for Linux to perform better while being virtualized on Windows Server 2008 Hyper-V. Microsoft's seeing that helping Linux to improve will help its own services to improve. To be fair, this helps customers of Windows Server 2008 more than anyone else at this time.
The reasons Microsoft did this probably are varied, but chiefest of them are economics and customer demand. Businesses are working to reduce costs in every area possible so as to keep their highly-skilled personnel, and sometimes this means consolidating hardware and software. Virtualization can accomplish this sort of consolitation. According to Tom Hanrahan, director of the Open Source Technology Center at Microsoft, "customers have told us that they would like to standardize on one virtualization platform, and the Linux device drivers will help customers who are running Linux to consolidate their Linux and Windows servers on a single virtualization platform."
On the same topic, Sam Ramji, senior director of Platform Strategy in Microsoft’s Server and Tools organization, added that "requests from our customers and partners were really the impetus behind [these] efforts. We are hearing more and more customers and open source partners telling us they see some of their best value when they deploy new open source software solutions on top of existing Microsoft platforms. Today’s release would have been unheard of from Microsoft a few years ago, but it’s a prime example that customer demand is a powerful catalyst for change."
Despite it being for Microsoft and their customers' benefit, it can't be denied that this is a good turn of events for the Linux kernel. A few more drivers that will improve virtualization performance can only be good, and who can complain when there are no strings attached with the GPLv2 license? Though this is the first actual contribution of code to the open source arena by Microsoft, the company has participated and helped several open source projects along already, and it's probably safe to say that this won't be the last contribution to the community. When asked what was in the future for Microsoft and open source, Ramji's first statement was, "we’re focused on building sustainable business strategies for open source at Microsoft." Essentially, if it's profitable for Microsoft's business, then it'll deal with open source. Can you blame them, though? Money talks especially in this age.