I have installed the 4.4.4 update about a week ago, or so....
So far, I have not noticed any major improvement (or decrease for that matter) in battery performance at this time. I am still running it through the paces, but am not holding my breath.
I must say it is very nice having a file manager that actually had write access to my SD Card. I much prefer Root Explorer (even without root access), but this new native file manager works just fine.
It is also quite nice to have a native flashlight now. All the third party flashlights seems to be sketchy at best (inappropriate permissions, odd network connections, etc).
Now if only VZW would approve the HTC FM Radio app.... Though let's be honest, that is never going to happen is it? If we had access to the FM Radio then we wouldn't be streaming. And if we aren't streaming, then VZW wouldn't be able to nickel and dime us for data. I guess being on a network that actually has great coverage means having to give up a few services that would never put a penny in their pocket.
Kratos