I've updated my iPad but will hold off on my phone at least until I have got my new MacBook once the Back to School deal starts and I know all my apps work as expected
As usual, my iPad & my Mac will be the only devices updated at first. my iPhones too vital for my day to day, to gamble on one of the apps not working (or working in DB1, breaking in DB2 or later). iPhone will get the shiny update around DB5/DB6