If you're a frequent ROM flasher (why does that sound mildly dirty?) and a OnePlus One owner, you might want to grab the latest build of TWRP. A Team Win developer says that it now supports Qualcomm's native encryption scheme in addition to Android's standard AOSP encryption. Why does this matter? According to Ethan "Dees Troy" Yonker and cited benchmarks, Qualcomm's encryption offers better performance when compared to Google's encryption applied to the same hardware.
...for slower encryption methods.
The hardware-based encryption offers an approximate 30% boost to read-write speeds over Android's software encryption, though it's still well below the performance of unencrypted flash storage. Apparently that boost is enough for Google itself to take notice, since some of the code commits between Android 5.0 and 5.1 indicate that Android will support Qualcomm's native encryption in the future. Because Qualcomm supplies the system-on-a-chip hardware for such a huge portion of mobile hardware, Team Win decided to get ahead of the issue - adding in this support was not an easy step.
The latest TWRP builds released specifically for the OnePlus One should support decryption of all current CyanogenMod and Oxygen OS releases. At the moment the latest builds of CyanogenMod (released and/or flashed after January of this year) support Qualcomm's native encryption method, while OxygenOS does not. You can download the latest TWRP recovery for the OnePlus One here.