We've had late dinner reservations many times and we were never rushed so I doubt BOG is any different. The one thing we did notice when we had dinner at BOG was the fact that they were pretty quick with the pacing of courses. I would guess that's because they have a huge number of tables and are fully booked every night.
Also, even though the park closes at 9:00 the stores on Main Street will remain open for an additional hour so you won't be the last ones out of the park.