Boston: Jacket Required

I'm off to Boston for a week beginning tomorrow. I expect some really great things to come out of a couple of conferences I'll be attending, and I'm also looking forward to seeing good friends of mine who are coming to Boston for a day so we can go to dinner on Tuesday night. We're going to Excelsior, which by all accounts is a great restaurant, although I'm always a little put off when the fine print says "Jacket suggested." I don't plan to wear a jacket anywhere else - certainly not to the conference sessions - so I haven't decided if I'm going to pack something that will get one use that week, or go without and feel a little out of place while dining.