As others have said, cheerful beats grumpy. Having said that, I am not a fan of announcements over the PA giving anything other than the necessary information. The best FA for me is the one that goes through exactly what needs to be said, as quickly as possible, without breaks in the announcement (e.g., turning the PA off and on multiple times during an announcement). I almost exclusively fly long-haul and if I am watching a movie, I like my interruptions as short and infrequent as possible.