There Are iOS 8.4.1 Problems
Note that there are iOS 8.4.1 problems plaguing iPhone 6 users.
In the days since the iOS 8.4.1 release we've begun to hear more complaints about the iOS 8.4.1 update. iPhone users have been complaining about battery drain, poor connectivity, installation issues, and a whole lot more. Thing is, none of these problems appear to be widespread.
The iOS 8.4.1 problems we've seen are all isolated to a few users. We haven't seen any major issues on our iPhone 6 models and there don't appear to be any widespread problems plaguing the iPhone 6 or iPhone 6 Plus.
That said, these problems are precisely why you'll want to be careful with the iOS 8.4.1 release. There's no way to predict what might happen once you have it on board.