If focused on BOG for the meal, then I'd agree with most of the comments above -- i.e., for a birthday meal, go with dinner. Dinner has a totally different feel than lunch, which is more of a cafeteria atmosphere, from the moment you order at a kiosk to the table where you sit. At dinner, the lights are a little lower and it's just a nice place to slow down and escape from the hectic pace of the park outside (whether your own hectic pace or that of people swarming around you!). When we had dinner there, we ended up sitting by a window where it was "snowing" just outside, which was pretty cool and not your typical Magic Kingdom meal experience. In all fairness, there are plenty of WDW restaurants I would choose over BOG, but if you're in the MK, don't want to deal with leaving to go elsewhere, and want a really neat birthday dinner atmosphere, it's a great option.