The Nexus 5X Marshmallow update in March (I think..?) that included fixes for performance issues in addition to the usual security updates resolved some of my long standing slowness issues. Unfortunately, with Android N, I'm experiencing performance degradation that's even worse than what I saw pre-March (or whenever it was) update. In fact, I came here just now to see if others were seeing the same thing, or if I was the only one affected. But regardless, that's been my experience.