A larger choice of alternative mobile OSs
A whole bunch of new mobile OSs, not built off of the Android code base, is ready and available on new devices now: Tizen (by Samsung), FirefoxOS, Ubuntu Touch, and my personal recommendation: SailfishOS by Jolla. The “not ready for Primetime” cliche goes for this one as well, for a number of reasons, but that doesn’t mean it doesn’t have a large number of happy users already. Both the company and the very active community are dedicated to their values of openness, independence, and privacy. I very much recommend watching out for the next release, SailfishOS 2.0, which certainly will see it much readier, possibly on the Jolla tablet, due to launch before the end of Q2/2015, or the Jolla phone itself, if you are ok with its mid-range hardware specs.