The developers over at XDA sure are fast and have done it again, this time bringing early builds of Android Lollipop 5.1 to the OnePlus One. Owners of the OnePlus One eager to get their hands on the latest version of Android can head over to the source link below to flash the latest version of the ROM now. The builds of Android 5.1 are based on sources from CyanogenMod's 12.1 branch, and are currently titled as a work in progress. A word of caution however, these builds are in extremely early phases of development and do not come without quirks. The developers for CyanogenMod work very quickly, so users can expect the various bugs to be squashed as the daily builds progress. Username "CraZY_BoY^" takes credit for uploading these builds, and reminds users in his post that he is only a builder. Basically he is not editing the ROM at all, but simply building CyanogenMod 12.1 for OnePlus One users to enjoy as there are no official builds for the public yet.
One of the current bugs listed on the XDA posting includes force closing of settings when attempting to select and order tiles for the quick settings pull down. Users of the unofficial CyanogenMod 12.1 builds will also in its current state experience Alarm force closes as well. There is not more information stating whether the alarm is working, only that it force closes. Furthermore, the stock messaging app will force close whenever a text message is received. Luckily the post details that if you use another app for messaging such as Google Hangouts, the force closes do not occur. Lastly, when installing apps the android package installer crashes although the app will install just fine.
To sum this all up, it sounds like these early builds of Android 5.1 for the OnePlus One are worth trying out. There doesn't appear to be any "show stopping" bugs, and the bugs that do occur seem to have easy workarounds. OnePlus one owners likely cannot wait for Android 5.1 to bring them improvements such as native HD voice calling along with enhanced system security and speed. Users in the thread on XDA are reporting mostly positive feedback, and the builds will only continue to get better with each daily build integrating commits and fixes from the CyanogenMod Github.