To beat any incumbent you need to offer better products. MS isn't just a Windows desktop, it's the server, terminal services, AD, DNS, DHCP, Exchange, SQL, IIS, .Net, Sharepoint and a whole hoard of other stuff that works, and works nicely together with very little effort. As much as the Linux fanbase would this not be true, there is no linux solution that even comes close to this. Sure you could cobble together a bit of this and a bit of that that sort does something similar, but it takes 10x as much effort, only has 1/2 as many features, and is a nightmare to support or troubleshoot when it breaks (or a new guy comes onboard and has to figure out your homebrew mess you created.