I'm sorry but you shouldn't be telling people not to upgrade based on a beta. For me, performance isn't much behind iOS 10.3.2 and that's pretty remarkable for a first beta. As for your mention of missing features, the phone either doesn't have the hardware for or cannot cope with the processing demand required, this is no different to features that were omitted in iOS 10. There is also no need for one handed keyboard on this device as a thumb can easily reach the other side of the screen! If you choose not to upgrade then that is your decision but please don't advise others not to based on misguided initial impressions and general ignorance.