Calling all HTC One owners

Just wondering how has battery life been for owners of the HTC One? I recently got my One just over 2 weeks ago now & the battery life for the first week or so was great, I was getting 8-10 hours on moderate to heavy use with brightness at about 45%, WiFi always on & mobile data (4G) use for about 30 minutes a day. But lately the past 10-11 days battery life has pretty much gone to shit. Even with power saver mode on & brightness down to its lowest I'm lucky to get 5 hours of moderate to heavy use. Has this happened to anyone else? Its really annoying not being able to get through a full day now without charging. Also I just updated to 4.3/Sense 5.5 about a week ago, maybe this has something to do with it?