I've been "using" the One for a little over a week now. I say "using" because the past few days I've been on vacation at my parents house where I don't get any cell coverage, so the One is just an MP3 player for the next few weeks. The only two issues I've noticed in my time have been the GPS taking maybe 5 or so minutes to lock on once I start navigation, and when I plug in headphones, the phone will sometimes play music for half a second before shutting off, though that bug has been more rare. Battery life has been great, and I also rooted and installed Greenify and Franco Kernel so I'm getting even better battery than stock.
Cyanogen is awesome, and I love all the extra additions. Before buying the One, I had a Nexus 5 running Cyanogen as well so I was familiar with some of the additions already. The two biggest things that aren't included on every other Cyanogen build are the camera app and the Audio FX equalizer. I haven't taken many pictures yet, but they've all come out great. The Audio FX makes any song sound like I'm in the studio the music was recorded in.
All in all, it's worth the wait for those that still don't have one, and definitely worth the $350. And I still don't have invites to give out
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