I'm happy the USB OTG is back and the phone feels snappier. Battery life (for me) is noticeably better after a significant decline with 4.4. Good that they fixed all the bluetooth volume issues I was having with my headset (basically one volume on the LG Tone+ and when connected to the car, voice notifications came into the phone and not out of the car speakers). Also looks like some notifications have had some tweaks, such as picture auto-backup now shows a thumbnail of some of the images that were backed up. It's a REALLY good update for me.
Only thing that bugs me so far is that when you remove the USB storage, you get a notification that stays there until the next reboot.