Given the fact that this is after all an unofficial port which happens to be in alpha stage its not like you will be able to use it as a daily driver. Wi-Fi, Bluetooth, mobile data, all sensors except GPS, camera and sound do not work in the alpha build however the team is likely to fix these issues as development progresses.
Since the port was achieved by making modifications to the ramdisk and kernel its likely that the user experience might not be as smooth as one would expect. Then again that’s the best that can be done until Google releases the source code and system images for Android L, which is bound to take a few months.
Flashing the Android L port for HTC One is the same as flashing a custom ROM. Do not forget to back up your data before proceeding. The port can be downloaded from here.