Is a different paradigm. The way you do almost anything is different from windows, from updating drivers to downloading programs. It's frustrating in the same way driving in the wrong side of the road can be frustrating, or going a whole day using only your non dominant hand.
I've tried to convince a couple people over the last few years to convert, and their issues always baffle me, until my brother tried for a week and I finally understood. It's just unlearned everything they've been doing for years, to do things a different way.