Just got it on my Z5 compact yesterday. Hoping it solves some of the nagging issues.
It has made my phone nearly perfect. I have been desperately wanting Smart Lock because the application Smart Unlock worked but it was just that, an extra application. Having it built into the OS is outstanding.
I do miss the ability to use a wifi network as a way to set the unlock, that was a nice feature of Smart Unlock. But Smart Lock in Lollipop has GPS location so that's at least something.
Plus it fixed a nagging issue I had: in my car I use bluetooth for music. My last phone it worked just fine, but until Lollipop the Z3v never showed the song info on my head unit. It would usually show the very first song but never update so I could not tell what was playing without looking at my phone. But now the head unit displays the correct info so I can skip and just look at it instead of the phone to see what's next! yay. It's the little things in life.
And in general, I love the new UI, I love that now a phone call doesn't completely interrupt whatever you are doing, instead just making a small dialog at the top of the screen if you are in anything other than the main home screen.