I got the GM last week on my 128gb 6S and its been laggy as f*** -- I have about 35gb free. Anyone else have this problem yet? Not so much any third party app as it is just the OS in general. I hate having to clean install these things but may have to if other users aren't reporting enough lag in the next few weeks for Apple to notice.
I was having similar issues. I did a clean install through iTunes and a restore from an iCloud backup immediately afterwards. Everything has worked perfectly ever since.