Supposedly there can be a slow down as the OS indexes everything. Who knows if that's true but I'm glad it is more responsive now. FWIW, I have an 8+, I went from a 6S to the 8+ and the difference was immediate. To be fair, I also bought the 256gb model so it might just be that with all that extra space, the OS could bloat to its hearts content and not have an issue. I wish to hell I could go back to Android but it's either rock an iPhone with work email or pay for a separate iPhone with work email...and that's just dumb, so back on the iPhone I find myself.