I got my OnePlus Two several weeks back. It is so far the best phone I have used till date. The features, build, price are very competitive compared to other flagships. At 4 GB RAM you can expect very good performance. Though I had some issues the speaker, it resolved automatically after few hours. The camera quality is very good, but it takes its own time for capturing the images. It offers high flexibility than any other phone. The home capacitive button doubles up as a fingerprint sensor, and also it can be assigned controls for double tapping and long press.
The other two buttons also offer the facility of launching commands on double tapping and long pressing. Another interesting feature is the alert slider button which can be used to change the mode of the phone; whether to Normal mode, Priority mode, or DND mode can be activated by sliding this button. It also has knurling on it which gives a good feel.
To conclude, although the maker has to fix some bugs that is causing several problems occasionally and the phone lacks NFC, it has a very premium feel to it at a cheaper price and it definitely is a flagship killer.