Anybody on here who's tried appears to have bricked their phone (myself included, see other threads). There are no known solutions to getting the phone usable again.
See these threads for more information:
http://forums.androidcentral.com/nexus-6-rooting-roms-hacks/501954-problem-side-loading-5-1-ota.html
http://forums.androidcentral.com/go...id-5-1-update-treating-you-3.html#post4289444
http://forums.androidcentral.com/ne...ricked-my-nexus-trying-side-load-5-1-ota.html
See these threads for more information:
http://forums.androidcentral.com/nexus-6-rooting-roms-hacks/501954-problem-side-loading-5-1-ota.html
http://forums.androidcentral.com/go...id-5-1-update-treating-you-3.html#post4289444
http://forums.androidcentral.com/ne...ricked-my-nexus-trying-side-load-5-1-ota.html