One big negative regarding Grandmas IMO is the fact that they serve Ultima as their sports drink. It has no sugar and 10 calories per serving compared to Gatorade with 14 grams sugar and 50 cals per serving. I'm sure Ultima is a fine beverage, but IMO it's not the best bet for a marathon.
So what's the solution to that? Well if you are my wife you can be thankful that I'll be leap frogging the race for her with Gatorade….I hope I can keep up. Otherwise I'd suggest carrying a few gels.
I completely agree with Ryan that you need to at least get something at every aid station. I'll also add that I'm also experienced in the end of the race “death march.” 🙂
Lastly pray that you don't get 2006 / 2007 weather conditions!