For example Quake 3 game won't work if you set it as Always On. I think when Always On then you have to insert the excluded apps manually in the system properties, I wonder why they didn't make it like a popup, then it would be very useful. There were few more examples here on the forum but can't remember them now, suffice to say it is a very problematic option, I wouldn't recommend it Always On for anything other than some serious servers. If in doubt just leave it default, that's what I do. Search on MS site for more info.