After using the beta 7 on iPhone 6s for last few days, I would say the beta is fine on some points and bad on others.
All the results below are after resetting the iPhone and then updating the latest backup from iTunes.
Pros:
1) Smoother than all the earlier beta's.
2) less app crashes
3) stable 4G network
4) faster processing in apps. ( I have edited a 124mb .csv file on the phone)
5) sync with iTunes on PC is more faster.
Cons:
1) Worst in battery life.
2) battery usage time and standby time is same ( pic attached)
3) iCloud sync from phone takes more time
4) switching over from mobile data to wifi is problem. It shows connected to wifi, but only connects when you enter settings app.