If it was a bad update, I would've not only not seen a performance improved, but a performance degradation. I DID see a difference; even if you have the latest device you will see a massive difference. Like I did. They don't need to inform people of anything, again, reviewers and beta testers are there for that. They're pushing out quality updates, especially these days, and they seem to be on the right track of making things even better than ever. It's not their place to make a PSA over slight performance differences of update to update.
They have even notified the public, IIRC, when the older phones were just too slow to accommodate the newer software.
Finally, if you have a phone that's just too slow to keep up, that's your issue - It's the same with Windows 7; runs slower on older hardware but FASTER on newer hardware vs. that same newer hardware running older software (say XP).
Just how tech goes sometimes. And not upgrading to a new phone to 'stick it to Apple' is silly. As software progresses, so does the need for more powerful hardware.