Reason #2: Microsoft has practices that would border the shady (what's new, right?). Case in point, Microsoft Genuine Advantage.
According to the web, if you're running a pirated copy of Windows, you could be reported to Microsoft. Nothing wrong with that, right? After all, it is their software; their proprietary code; their property. But what if you found out the tool was installed without your prior knoweldge? Pirated or not, that gives me the creeps.
Using Ubuntu, I love the Synaptic Update Manager, because it tells me in explicit detail what is being installed. I don't read through pages of EULAs, as I would in the Windows updater. Rather, I am told exactly what is being installed on my system, and more importantly, I can refuse certain updates as I please. In other words, Ubuntu Linux is straight-up with me on what is going to be installed. Microsoft, on the other hand, would rather I never knew.
Even Microsoft admits that it needs a better way to inform its users what is being updated and installed. All I have to say, is if you are a Microsoft user, you better make the switch to Linux before Redmond and Co. decide to start snooping your files for financial and personal information and reporting them back to HQ.