Loved how using a backup from the same day I was back on Lollipop with all my apps etc as they were. Most excellent.
So I have been very impressed with the Android M Preview 1, it's extremely stable on the Nexus5 and almost a usable OS for every day use.
The big problem I had was that every now and then I would not be able to answer the phone. Either the screen would stay black and just ring, it would not let me swipe to answer or I did answer and the person calling me could hear me but I could not hear them. The last time this happened was an important call so I decided I would ditch M until it properly arrives.
I don't feel I am missing much going back to Lollipop and the fact that it is so stable gives me hope. Although I expect Google to completely stuff it up on the Nexus 9 like they did with Lollipop so my 9 will have to wait a whole lot longer.