Ya, I'm thinking the 1020 has some issues with this build.
I installed on my 1520 (daily driver) 4 days ago and have been very happy with it. Fast, Responsive, and good battery life (maybe down slightly but not enough to bother me). It has a couple quirks (apps that refuse to load, flashing quiet hours, but nothing too frustrating).
My experience was so good that I decided to install on my wife's 1020. I'm rolling it back to 8.1 as we speak. The battery life was terrible (though to be fair I didn't give the hard reset a chance). I had trouble with bluetooth and cell connections. Texts were slow going and out and coming in. MMS wasn't downloading (again a caveat, I didn't dig into the settings on this). Apps were crashing on a regular basis. I was having trouble adding accounts. Overall lag, etc. Put it all together and it just wasn't worth the headaches. My wife is fairly tech savvy, but not as much as me. If it was my phone I'd stick it out and perhaps I could find solutions to these issues. But with her's its just easier for me to roll back to 8.1 Not complaining. It's alpha software.
I'm just thinking MS might have a way to go to get this running smoothly on phones with older internals.