This mobile has both its pros and cons. Let me start with the former.
Its build quality and feel in hand is absolutely top notch. It looks the most premium out of all the phones released by oneplus and more so with the limited edition ceramic version.
Another big plus is that it has a 1080p super amoled display. The screen looks beautiful and saves battery with its specially designed black theme.
Its powered by 2014 flagship snapdragon 801 along with 3 GB ram and hence delivers excellent performance.
Now move up to cons
It has strictly average camera. In this price band you will find phones having much better camera. It has small battery which dries out quickly despite having amoled display. OxygenOs isnt the fastest and is buggy. Also the ceramic version is overpriced. Even for the normal version you will find Mi4 boasting of same hardware and better camera for much much cheaper price.
Verdict
If your highest priority is how the device looks then go for this phone. Otherwise mi4 is much better option at a lower price