The Lollipop load doesn't seem to have anything *wrong* with it that I've found so far and it's got several things *right* on my Nexus 5.
It *feels* a bit faster, although some of that may be actually psychological with the new animations. Battery life doesn't appear to be worse than the KitKat load. Of course, I started out with voice recognition turned off from KitKat -- I don't know if that improves in Lollipop or not.
The old e-mail program has been dumped in favor of the new GMail interface which is at least as functional as the old stock e-mail interface. And unlike the old interface, it hasn't yet managed to tell me that I have a negative number of unread mails yet. :)
And Hangouts seems to have been fixed as a text messaging interface. The version in the initial KitKat / Nexus 5 release didn't work at all, to the point where I downloaded 8ms to replace it. I jettisoned 8ms yesterday, as they started throwing in ads. Ick.
Having the option of showing notifications on the lock screen is handy, as you can glance and put the phone back in your pocket without unlocking it.
In the amusing, but handy in a pinch category, they've added a flashlight function to the load that activates the camera flash as a constant beam. It's not a *lot* of light, but if you drop your keys in the dark, it gives you the handy opportunity to drop your phone to join them -- excuse me, to find your keys.
Wi-fi connections that aren't available no longer show up in the Wi-fi setup, which is nice.
Anyway, from a features POV, it's evolutionary, not revolutionary.
But the speed seems good, so I'm sure there's some serious rewriting down in the kernel.
And that's the early report.