I'm testing build 5.1 since last night, so far loaded, updated all apps working smooth with a few hiccups.
At one point,sound stopped working, reboot restored it.
Google play not responding sometimes.
Transparent status bar build.prop workaround.
Boot time faster than aosx.
call function not yet tested.
WIFI seemed to not work even when the icon was showing, so went to Wifi advanced settings, turned off the Wi-Fi optimization feature.
avoided installing gravity box for now.
1 Calls are working fine,
2 Sometimes cannot exit an app using back button, need to touch home instead,
3 Battery 8 to 9 hrs avg use for 2 days now (in aosx, same usage and loaded apps I get around 12 hrs)