Many places allow you to set your own hours when things are good. The real questions is things like if you get in early to beat traffic and something happens in the afternoon can you still leave without being considered "not a team player" for not "just fixing that thing we need for the meeting tomorrow"? Is the same true if you didn't get in early?
Not many things are so urgent they can't wait until the following day. But if something like that did come up, you could just leave at your regular time and continue working at home to fix the problem.
