It's a joke. Everyone said that when the beta was out and people complained about lag. Now that the final release is out... everyone is like "It lags!".... well yeah it lags... we tried getting that fixed during the betas but nobody cared.
People say "ah but it's just a beta, wait for the GM" and then they say "it's the first release, what do you expect? Of course it will be buggy, all new software is like that and you need to give Apple time to fix it"...blah blah blah. It's the same every single year since iOS7. It's the norm now, lousy software that people have to live with for months until Apple sort of fix it only for the whole merry-go-round to start again the following September.
To think, this was supposed to be an iOS release that was low on features but big on performance and it needed to be after iOS8...but no, and what did we seriously expect.