I'm just going to say this:
I've been using iOS 9 on my 5c since June 8th when it was released at WWDC. It has evolved (A LOT) since beta 1. As many have said, indexing is a major part of iOS, and with a new X.0 release, that takes time. Performance will suck for a while, and no, there's no exact estimate of when it will get better. On order for a proactive assistant to work, it requires mining (in a good way) through all your data to provide relevant information in the future.
I get it, Apple says "it just works", but give it time.