Having seen L in action a bit here and there one thing I noticed is that, for the most part, the haphazardness of Android is still there. There are some notable changes in parts of the interface, but the biggest difference, from a UI perspective, is the skinning/color schemes. Much nicer to look at, but still has a lot of the UX faux pas that continue to make Android a painful experience for some, such as myself. Now, the whole ART and AOT thing will definitely help the OS be more usable in situations where it struggled before, but there appears to be a host of bugs to go with it, which is not uncommon.
Android is still the tinker's OS. It's best for those who want to set there electric bidet to wash their bottoms at a specific temperature that you can control from work, while piloting a drone remotely to watch cats pounce on mice outside. But, for many, it's still a sensory/information overload situation with the OS. It's why Apple still has a good size market share in the US. Windows is more of type of OS for the power user who's tired of changing and tweaking things all of the time. For someone like me, who still occasionally drives the command prompt, it's an oasis away from complexity without giving up too much capability. My smartphone simplified, if you will. That won't appeal to everyone, especially hard core techies, but each of the three OS' have an audience. I suspect a few years from now we'll see WP around the 20% market share (US) range, along with Apple, and the rest will be Android. For me, I just want my choice to be viable long term. Giving up webOS for the choice of iOS or Android just plain sucks. WP softened that blow some. I don't want to be in that boat again.