This has been out seemingly for ages, but I just got it OTA on my old Nexus 7. First impressions: a bit snappier and easier on the battery, cleaner UI (not sure I like the new keyboard though), fugly default home screen background.

there's a dark keyboard in there too if that helps any.

The full rollout seems to have been delayed because of a memory leak, I wonder if they've fixed it yet. If not, you'll find after a few days that the system has grown too big and starts slowing things down and stuff, needs a reboot.

So far the main annoyance I have with it is that they've done away with lock-screen widgets, which apparently "didn't really catch on". It means I have to unlock to use the Yatse XBMC remote controller app to play/pause/skip, rather than just using the widget. Dammit.

The previous version was getting progressively slower for me anyway. Maybe I should reboot more often, I only ever reboot after a version upgrade and once when it mysteriously crashed.

Now I've had a chance to use the keyboard a bit, I think I like it better than the old.

Can't you turn off screen lock (mine has "none" as an option)?

That's a PITA to remember to relock though.

Smart unlock + setting up Home and Work as safe locations mean I don't often have to bother with unlocking it when I'm using it for that kinda thing. Although you do still have to swipe so I guess that's an extra input for you.

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 think I have some other issues too.

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.
 

I started having problems with Chrome running really slow, general unresponsiveness of Android, and lock ups, so I'm trying the clear cache method suggested here: http://www.gottabemobile.com/2014/12/15/moto-360-android-5-0-1-update-rolling-out-today/

Yup, it definitely helped.