A few years back we took a *bonus* trip to WDW b/c my husband had a conference at the Boardwalk. Since this trip was pushing our vacation budget for the year, I had to minimize the money spent on Disney food. What surprised me were some of the non-food benefits to bringing our own.
1) Having a more pleasant experience: At Blizzard Beach, I brought a soft-sided cooler filled with cans of soda, bottles of water, sandwiches, and fruit. I also brought in salty snacks like goldfish and pretzels. Honestly, I think this is the best way to visit one of the water parks. First of all, my kids got to eat when they were hungry without fighting the crowds at the food pavilions. (The crowds get long at lunchtime.) Secondly, due to the heat, lighter food was more enjoyable than a hot dog, fries, etc. We had a lovely shaded spot where we had set up for the day, and it was very pleasant to take a break, lounge at our chairs, and enjoy our food and drinks. To keep my kids from feeling overly deprived, I promised that they could each pick a Disney treat or snack later in the day, and by 4:00 or so, there were very little lines and everyone enjoyed their ice cream, dole whip, etc. The convenience and relaxing nature of bringing our own food, was great and something I would absolutely do again if I were doing a water park day, regardless of budget.
2) In the parks, it can be a real time saver and morale booster to have our own food on us. Having snacks in line has been great. We have had "theme park commando" days where snacking in line has saved a lot of time. Also, bringing our own food has helped keep everyone happy, when someone has needed food and needed it now! I'll never forget the time we got in line for Mission Space with a posted standby wait of 20 minutes and we ended up waiting well over an hour, for whatever reason. Everyone got hungry, so I pulled out snacks that we ate in line. No one likes an unexpectedly long wait, but no one got hangry. Over many years of trips, I have learned to always have a good stash of snacks on hand.