Quick thoughts:
Linux on the desktop should be rebranded as Linux on the laptop. I haven't used a desktop for at least 6 years. This relates directly to what my main impression is: For power users, using Linux feels superior in almost every regard, except hardware support.
This is bitter-sweet, because installing/purging apps effortlessly from repositories, keeping a system up to date, and having good usability is fantastic, but the paper cuts are there - brightness adjustment doesn't work, skype video failed suddenly, can't configure touchpad fully (disable tapping, use side-scrolling, etc.). Battery life is noticeably inferior to Win/OS X.
Also, buying PC hardware is a nightmare - way too many models, with terrible nomenclature. Models with entirely different processors, etc. have almost the same name, etc.
I dream of a "Linux Apple" - a company that sells a small but smart range of laptops (even at a premium) with a selection of hardware that guarantees that a major linux distro will run on it without paper cuts. Companies like System76 fail - their machines are too heavy and the battery life sucks (same for others, not singling them out).