There is so much new with this phone I have to continue from where I left yesterday.
In addition to huge display the body of the phone is quite sleek overall. The material is smooth which, in addition to it's size, makes it quite hard to keep at hand. It feels like it could slip out from my hand at any moment. So case is a must have with this phone. It offers double protection when you are less likely to drop it in the first place and protecting it even if you do.
I opted for Oneplus' official carbon fiber style case. It leaves the curved edges nicely exposed making the edge gestures easy to execute while still protecting the screen and corners. It also provides some much needed friction while holding the phone.
Only issue with this case is the fact that it's actually designed for the non-T version of the phone. While the phones are physically almost identical there is one small difference: the autofocus module which used to be integrated into the camera module in the back of the phone is now located left of it. So it's left covered with this case. I just need to do some diy modifications to make it visible again.