My supervisor is very easy going and doesn't have a problem with us being late. I like to be timely, so if I m running late then I don't do other stuff to make myself later just because I'm late anyways. There's a daily design critique meeting (or almost daily, depending on what people have gotten done) that I attend at 8:30 (when our workday is scheduled to start) and I think being late to that meeting is rude to everyone else who made the effort to get in on time, so I generally get in early every day.