Does exactly what it says, and doesn't seem to slow down YouTube contrary to what the previous review claims.

Great but slows youtube bandwith down a bit.

Never had a problem with it, it's pretty reliable :)

I just wanted to enable theater mode by default and that's it.

I have never had a problem with the addon, but Avast gave a popup that says that this addon has a bad reputation and recommends I remove it.

You might want to check on that, I couldn't find any information in their forums but I won't be the only one getting that notification.

Works as promised. No regrets.