GMFB's used to be the only means of getting into the park before it's scheduled opening time but only certain Fantasyland attractions would be open. We would use it just for getting into the park early to get Fantasyland done before the crowds hit it.
The breakfast is of the same standard as that at the Cheyenne, so if you're staying at Sequoia Lodge, you're downgrading a little, there isn't as much choice of fruit juices, plastic knives, forks and paper plates, it's a bit of a bun fight really too. IMHO
With EMH we've found it easier to have an early breakfast around 7.00 - 7.15the hotel restaurants are quiet then and even if you've been allocated a later breakfast slot, you're not going to have a problem getting in. If you can be at the park at opening time then 8.00 with EMH, you've 2 full hours before the crowds hit, when the park is busy these 2 hours are worth their weight in gold.
If you're not going to breakfast early at the hotel then try and choose the latest GMFB time which I think is 9.45am that way you'll still have had almost 2 hours to enjoy the park.