Honestly for the Specs and Size. Its a "YES" for me. I had HTC One X for 2 years but the thing I don't like is the Battery life. Was thinking about Nexus 5 or Moto X which has very similar specs but i go for the "size", "battery" and IP57.

Z1C last me average 2.5 Days with 4 hrs screen time. (For normal usage)

Regrets on Z1C was only the screen had ASF (Thin layer of film to prevent glass shutter) which easily get scratch. (Solution - Get a good screen protector, prefer a Glass with 9H)

Liking - Battery, Water Resistant, Power, SD Card Slot, Camera and a slick design.

Not talking about the software side but I read that Sony quite reliable on updating their software + Firmware. Currently on 4.3 and likely to get 4.4 kitkat (Hopefully the battery will get better then).

Hope this helps!