I only upgraded my Nexus 5 to lollipop about a week ago (a custom ROM).
So far I'm not really a fan. I hate how notifications are handled. There's standard "Silent" setting - have to use a "priority" notification setting to make it silent.
I don't mind notifications on the lock screen but I have the setting to hide private info (which hides who a message/email is from etc), that's all well and good but the fact it shows "private info hidden" just seems ridiculous, it doesn't need to say that.
I have to force close a certain app twice a day (radio app that doesn't turn itself off when disconnecting from Bluetooth - though thinking about it I might be to do something with tasker) and it's more hassle to get to the app settings to kill it. Used to be able to tap-hold the app in the notification pull down or app switcher thing and you could go right to app settings.
Having to swipe to get to the pattern unlock screen is a pointless gesture.
I have had it on my 2013 Nexus 7 for a while now and while there are some great new features and layouts I have had many slow down and unresponsive app problems (mostly in Chrome) My Nexus 5 had the same problem until I cleared the android cache partition but it didn't work for my Nexus 7.
It's a step forward and very easy to pick up but I am struggling to see where they are going with Android. I have a Nokia 920 for my work phone and an currently warming greatly to windows phone 8.1. I miss the widgets but its much more responsive and actually works well in a MS Office and online environment. Cortana is great as well I find I am using it more and more instead of pressing buttons.
