Same issue here. Came home from work yesterday (16th) to find it had updated. Watched about 20-30mins of live TV and it rebooted, then shut itself down halfway through the boot. Today (17th) it just rebooted again while I was watching a recording. Luckily something had just finished recording about 15mins previously, or I would have lost that too.
A bit reluctant to reset at the moment, I will if I have to, but I'd like to see how this pans out first, as it's looking like a bug that's affecting a number of users.