Did you shutdown both iPhone and AW, boot up iPhone 1st, wait for all thing booted, then boot up AW?
My work fine after upgrade, but I always follow above process to ensure AW with 2.1 get to sync with iPhone Wu latest iOS.
Also there could be 3rd party AW is NOT tested and updated to 2.1, which might eat more battery.
You could find out which one by only run Apple native app, then turn on one at one time and monitor.