I've been getting iOS betas since 9.0, and this recent 9.2 Beta 3 is the first time I've commented on these forums about it (I haven't found anything incredibly annoying enough to post about). I have an iPhone 6S Plus. With this recent beta, after one full day with it, I have a huge difference in battery life - in a bad way. Off the charger at 7am, by 10pm, I was down to 71%. For reference, I don't spend a lot of time on my phone during the day, and for my nearly 2 months with the 6s so far, I've always had around 60-70% when I get home at the end of the work day. I have not used my phone any differently than I always do. Just my experience with this beta so far. Otherwise, everything is fast and fluid, and an overall great experience.
I'm assuming your 10PM is a typo and you meant AM. Because after 15 hours, if you are still at 71%, then I think you are doing pretty dang well.