In LL#43 Joe mentioned that one isn't likely to dual-boot on a phone; that's definitely true and not really possible on most devices, but! If you have a supported device and are geeky enough to want to try it, MultiROM actually makes dual-boot quite simple.
In fact, not only does it make booting and such quite easy (all you have to do if you have a supported device is make sure it's unlocked and rooted, then install the Android app from the Play Store), but it even makes adding Ubuntu Touch quite trivial. You literally just select it from a menu and tell it to take care of it! This should work pretty much perfectly on most Nexus devices and similarly widely supported devices, although I've only tried it out personally on my old Nexus 4 (which I triple-booted with Android, SailfishOS, and Ubuntu).
On the broader point though, Joe is definitely correct. These days it seems like Android is in the mobile space where Windows was just a few years ago in the desktop space. That was even a recent thesis of an essay by Vlad Savov up on The Verge: http://www.theverge.com/2015/6/8/8748359/apple-music-android-windows-wwdc-2015