I've been using my brand new Purple Z2 for the last few days and I must say its a fantastic device. I'm coming from a Nexus 5 which I got since day one.
With the Z2 I downloaded the Google Now Launcher APK and got all my apps installed and now its almost exactly how I had it with my Nexus 5 (Google Now hot word does not work). Unlike my Nexus 5, my Z2 has amazing battery life and camera in addition to being a water resistance device.
I'm not using any cases or screen protectors, but I think I'm going to get the Spiegen slim case for it as the phone can be slippery at times. For those who are wondering about how it physically feels compared to other phones I can say that at first the Z2 can feel a bit cumbersome due to the hard corners and edges of the phone. But after a few days with the phone I hardly noticed it at all. I also notice that the volume keys don't provide much feedback. For other phones you can feel the 'click' of the volume presses which lets you know its being pressed. For the Z2 you'd have to look at the screen or hear the change in volume to know that its being pressed.
My personal concerns with the phone is the flaps that protect the sim/sd/usb plugs and how it will hold up over time. I really like the Z2. The battery life alone is enough for me to get the device. For those who are planning to get the Z2 I recommend getting a memory card. I use the Google Camera app and each photos are about 5-6MB in size.
That's it for now.