hiya! I ate at the BB for the first time on 8/13, so lets see if I can answer some of these:
How much in advance do I need to make a ressie?
I made mine literally a week in advance and got a good 5:20 seating. I'm not sure if there's too much concern on when to make them unless you're going during a high-crowd time.
Is it possible to split a plate? (It seems like the portions are huge)
Yup. I believe there's $12 dollar split-plate fee, because that way you'd both get a salad or gumbo, as well.
How long does it take you seat you if you have PS?
We had a PS for 5:20 pm, arrived a 5:00 because we were hungry and wanted a waterside table. We requested a waterside table, and the hostess said it would be 20-30 minutes of a wait. We were seated at 5:15 pm, 5 min before our reservation. They really try to move people in and out quickly, so the wait wasn't really long for anyone.
Did you like it?
We loved it. My dad and I had a waterside table, not right in the center, but we could see the loading area for POTC and enjoy the boats without being distracted by them. My dad had the chicken, and I had the short ribs, both were great. He had the chopped salad, and I had the gumbo, again both were great. We finished our meal off with the famous cookie boat. It was well worth it, especially the BB potatoes!