Re: should I install 5.1.1 upgrade
By following the procedure described on cultofandroid.com/63876/install-android-4-4-3-nexus-5-nexus-4-nexus-7/
I just downloaded 4-4-4 instead of 4-4-3 from developers.google.com/android/nexus/images
I have gone back to Android 4.4.4 since my device became unusable (slow!!!) after upgrading to Android 5.0 and I couldn't notice any improvement with the incremental updates from Android 5.