Desktop linux - still not there
Whilst I use Linux for many things and love it. On the desktop, even in the latest funky supposedly "idiot-proof" versions, it is still a million miles away from being actually useable for the mass public and so called "idiots".
See the problem is you still need a degree in Geekdom to configure the damn thing for your particular hardware, and even then support for many bits of kit is frankly "alpha" quality (WiFi and laptop support in particular).
I keep trying every now and again, running Linux on my laptop. It's just not there. Still. The basics work out of the box and looks nice, but half the hardware is just not supported and involves a lot of googling very technical geek forums for help. I got hacked off eventually with things like WiFi connections that take an hour to establish and then drop again, flakey touchpad and keyboard input, "updates" that corrupt USB drives, and went back to XP (which when kept pretty much to the basic install which supports everything out of the box, and avoiding the likes of system killers like Norton, then loading up loads of open source software like Firefox, Thunderbird and Open Office, works a charm).
Sure, when it comes to hardware and Linux you can just buy stuff you know is compatible. Indeed, that's called an Apple Mac ;-)... and of course you pay through the nose for the work that has been done to ensure it works with only that hardware. What people fail to realise with Microsoft is their software has the immense task of having to run with just about every bit of hardware that exists. Linux is always playing catch up and depending on 16 year old Russian geeks in their bedrooms, and Macs are more like games consoles with fixed hardware. All valid for their purposes, but there's a reason why MS has an OS on almost all desktops.
Then of course there is the development environment. No question there. MS all the way.