Having some experience around the TV/movie industry. I can back up some of the comments here. Julianne Moore was mentioned a couple of times and I can confirm she is absolutely lovely. Kim Cattrall was very nice too. An extra told me of how he was filming in a hotel and happened to know the manager. A good looking blonde woman came over and joined the conversation and they had a pleasant chat. Later when he went to film the scene he realised who she was. He had no idea.
Pierce Brosnan seemed pleasant enough but with a tendency for sarky jokes. Jonathan Rhys Meyers (Henry VIII), very pleasant and unlike other actors would queue in the studio canteen like everyone else despite having a nice trailer to hide in.
Haven't really seen bad behaviour. But had heard that Mickey Rourke was obnoxious and actually actually trotted out the 'Don't you know who I am' line.