it doesn't look bad if you can't make the dinner, to answer tayshaun's OP.
the dinner is mostly for you, believe it or not. remember, this whole thing is a two-way process. you wouldn't have been invited if you weren't wanted there. you are there to learn as much as you can in a short period of time about the kind of people you're going to be spending a good part of the next three to four years with. yes, you are on display, but so are we. it is a good time to have a honest conversation about what kind of cases you'll do, what call is like, and probably most importantly to see how the residents get along in a social setting outside the hospital. it's okay to let your guard down a little. we're not interested in hearing all the pat answers you've practiced on the last 9 interviews. we're there to get an impression of you, and vice versa. you won't remember the specifics, probably, of who you met. but, you should walk away with a general impression. "do i like these guys/gals?" is this the type of crew that's going to get my back and help me out? that's the kind of thing we're looking at.
so, not going to the dinner is a missed opportunity, nothing more. you should try to go. it shows effort, if nothing else. it's not going to be held against you if you don't. but, it's a missed opportunity. think of it that way.
good luck to everyone this year, if i haven't said that already. it'll be over before you know it. and, it should be a really fun time. you're about to begin your career before you know it. and, that's an awesome thing when you stop to think about it.