I like things that are mainstream and more obscure. None of those attributes tend to factor in though. It depends on the problem. Saying that I occasional have a bias in selection for mainstream which is justifiable. Mainstream in Open Source means more tried and tested, more contribution, more community support and a larger talent pool to hire from. It's not always good. Some things get massive contribution, even too much that quality goes out the window and you have a maintenance nightmare. On the whole though, mainstream tends to be alright.
"The whole Mir hate-fest boggled my mind - it's free software that does something invisible really well."
Actually I got really annoyed at this. Not specifically at Mir. At the whole there's always two things to choose from. Wayland/Mir, Systemd/Upstart, MySQL/MariaDB, oi.js/node.js, Electron/nsjw, etc. Choices are always annoying. Node.js managed to fix things. For a lot of things I find myself avoiding being an early adopter and wait to see how those things work out first to see if they merge or there can only be one.
There are two things I really hate. Bandwagoning and the unique/superior obscure tool obsession. You often see spikes in tech use due to bandwagoning that then drops as the language turns out to be too much trouble but then you still have the lingering stench of it because of a bunch of legacy products that used it. Bandwagoning can be linked to the other thing. Often someone will want to learn an obscure and often over complicated language so to not have competition and because they believe a theoretically superior (perhaps potentially than actually materialised) tool will offer them that. It will make them special or something. This can happen with new tools but ironically everyone has the same inclination so you get a burst of them. Then when they all realise that actually this boat is quite crowded they all bugger off to go master a variety of other obscure languages like Haskell, Erlang, Prolog, Lisp, Ada, R, etc. All of them though secretly dream their language will suddenly become famous and that they'll be the master in it or at the forefront. I just stick with what works well for the problem rather than some new fangled technology then adopt something when it becomes mature enough and suits the problem well. If language A is the traditional choice for domain A, then language B comes out claiming to suit domain A better, I can't really know that without a point of reference, such as language A, except when language A has been used in domain A a million times but language B ten times then I know that language A is a pretty safe bet. Don't get roped into being a guinea pig more than is necessary or that you really have the time for.