Phone is great. For $ 300 you can't go wrong. Easily customisable to suit your preferences.
Compared to my S5 .... the S5 is the better phone (costs twice as much) .... will switch back to the S5 on my travels because of the convenience of being able to switch batteries as well as the S5 is waterproof and can use an SD.
Otherwise, the OnePlus is a very fun phone and I haven't even started really toying with it yet. Battery life is also amazing .... but it is a brand new phone so will give it some time to see how it stands up.