A big change that I have noticed on my iPhone 6 plus after updating to iOS 9.1 (public beta) is that the safari tabs don't reload each time. Clearly then it was not just an issue of RAM if the new OS can manage this with just 1 GB of RAM. Another cool feature is the ability to edit attachments natively in the mail app , just like preview on the mac , including signing your name, highlighting etc. Not seen this mentioned in any of the iOS 9 reviews on the net