I just had my series 4 44mm GPS model for one day, because my old series 2 has been upgraded to 5.1 beta 1, I updated the new series 4 too.
Then, the battery life had been, horrible. Literally 10% power draw for 1 hour? So DON'T accidentally upgrade to the 5.1 beta yet!
Then, the battery life had been, horrible. Literally 10% power draw for 1 hour? So DON'T accidentally upgrade to the 5.1 beta yet!