We had reservations for 9:20 and arrived around 9:00. They sent us up but there was nowhere to sit so we wandered around out on the observation deck for 10 minutes until our table was ready. We had time to order our meal, try some of the great tastes of wine (they allow you try a small selection before you choose!) and finished our appetizers just when the fireworks were ready to begin. Unfortunately, they brought out our soup and salad so I let me soup get cold while I went out to watch the fireworks. Fabulous! The soup was still very good but I wish they would have held it a few more minutes to accomodate the fireworks. We could have seen them from our table but it was much better outside. As long as the weather is nice, I think you'll want to venture out.
I guess I'm saying you should try for a bit earlier or a bit later. But, of course, I suppose it will always depend on the wait. There was a family of five there that was furious they had been waiting for 30 minutes while hubby and I were seated almost immediately. Just the luck of the draw. But it looked as though there were many table there who had already finished their meal and were just hanging out until fireworks. I think if you get too close to time, you take a chance you will not get to even be seated until after the fireworks.