5.1.1 Performance Experiences

Hey guys, I just saw that 5.1.1 has been available for my N915G for some time now. I would like to ask how people are feeling about it in terms of performance? I was on 5.0.1 awhile back and it was so laggy and slow that I eventually downgraded to 4.4.4 (at times, I wouldn't even be able to answer calls because the phone would ring but the phone was so laggy that the screen wouldn't turn on until after they hung up).
I'm very happy with the performance of 4.4.4 now but I do like the features in Lollipop so I just wanted to ask if it's safe to jump back in? I heard that it's not possible to downgrade after flashing 5.1.1 so I need to be sure before taking the dive. Thanks a lot in advance!

[Q] Any experiences with bad replacement screen/digitizer draining your battery?

I've recently changed my cracked screen (to an authorized LG service center) and right after that my battery started behaving strangely. At this point I'll be lucky if the battery lasts for 2 or 3 hours.

I was about to change the battery too, but then I remember reading in a review for a Nexus 5 aftermarket screen/digitizer (before deciding to go to an authorized center I was thinking about changing the screen myself) that a user had bought one and after that his battery drain was getting worse day by day.

I can't seem to find that review anymore, but that behavior is very similar to my phone.

Do you think it's possible a low quality replacement screen can ruin your battery? Did anyone have an similar experience?

I'm just trying to figure out if something went wrong when the service changed my screen, or it was just a coincidence.