Here is my experience from 1/10/11; a slightly chilly but pleasant Monday evening for the lone show of the day at 8:15 (note the park closing time was 8:00) I know many (including myself) have/had questions about how busy this show would be in the off-season so I'll share my experience/observations.
Meal
Since it was DW's birthday and our first time viewing the show, we selected the Premium dining option at Wine Country with a reservation for 6:00PM. DW has eaten there before and liked it, so we chose it over Ariel's. We both ordered the same thing (roast beef); mine was pretty good while her's was rather putrid (EXTREMELY dry). Kind of disappointing, although we were mostly interested in the show. I rationalized the cost as being nothing different than paying for orchestra seating when Beauty and the Beast came to town. Salad and dessert were both very good though. The meal seemingly took forever for some reason (seated @ 6:10....left at 7:40PM).

We were hoping to sneak in a ride before lining up for the show, but service was pretty slow at dinner.
Show
Since we left the restaurant much later than expected and didn't have time to see any other attractions, we just headed over to the viewing area for WOC. We got there around 7:45 and walked right down to the very front of the Premium viewing area. There were no lines to speak of for the Premium area or for the other areas. We positioned ourselves at the railing right behind the wet zone area. Note that we were on a tier above the wet zone, so we were not obstructed by guests in front.
During our walk to our viewing spot, I noticed there were several open spots remaining in other seating areas. Not just scattered individual spots, but entire rows. Hardly the frenzied cattle call that I expected. After the show, I took a stroll around to survey different viewing points. There are many excellent points from which to view the show outside the premium area and several of these points were still available within 30 minutes of the show
on this particular evening.
Summary
For the first time seeing the show (which was spectacular) and given that we had a special occasion to celebrate, I think we made the right choice to guarantee a decent viewing spot with the Premium dining. However, if we return for future shows under similar conditions (non-weekend, offseason, cool evening), I'm willing to take my chances with a fastpass, picnic meal, or even by finding a spot on/near the bridge without any pre-reserved locations. Of course, we don't have any young children in tow, so we are a bit more versatile when it comes to looking over and between people in front of us.