I have an Apple Watch 3 running 4.3 (15T5212a) and I have noticed the battery draining a lot quicker than normal. Usually, I can get at least 2 full days without charging it. I am not extensively using the Watch. Yes, I am aware that "beta" versions are not stable releases and there are hidden bugs. I may wait to install watchOS 4.3.1 or I may not wait.