It's still early days, but I'm finding the Lollipop update to be a massive improvement over KitKat, the phone feels MUCH more responsive, and the battery life seems to have improved, though today is the first day I'll have started with the new software and a full charge.
The lag in the UI seems to have gone completely though which is fantastic. I had a few issues with KitKat being slow to respond sometimes.
I installed LP (German) over the weekend so its early days here too.
I'm not too convinced by the new OS though. KK was near on perfect for me in terms of smoothness with daily use. Lollipop whilst I admit is stupidly smooth has it's fair share of quirks.
* Contacts and Maps apps crash quite frequently.
* Recents menu still has a 1 second or so pause before it appears, so no change from KK.
* Batterylife thus far (too early to say tbh) seems to be no different to KK.
* Like KK Apps, can't write to the extSD card - I thought Lollipop was meant to change this. Got to root it seems to get by this.
* Too much forced Google app bloat (News, Hangouts, G+, Play Music, Play Books etc) - whilst not a OS problem, I'd prefer something called choice.
Whilst the UI and the little transitions on UI elements is all nicey nicey, there have been the odd stuttery menu transition moments on bloaty apps like YouTube and Play Store.
I am badly missing Xposed though as it allowed for a lot of tweakage and to make that awful TW coloured notification pulldown all black
