It's luckily so easy to downgrade back this time around. Just option click in iTunes and select the 6.1.4 IPSW and that's it. I've done it a few times now.
For some reason, at first, my battery life was so awful. I put it down at 93%, went to take a shower, came back and it was at 74%. It was really bad. Then afterwards I used it a bit, drained the battery, and charged it up to 100 again using the wall charger rather than the USB, and now, after quite a bit of standby and usage, it's still at 100%. The only things I changed were the settings for background updating or whatever and revoked Weather's permission to use my location as I noticed it updated a little too frequently.
Anyway, try charging it using the wall charger (an iPhone specific one, not iPad etc) rather than your computer if you haven't already. I've noticed in general that my battery always lasted longer when charged via wall outlet rather than USB/iPad charger.