You should go to extra morning hours and then leave that park about 2 hours after the normal opening time and visit another Disney park without Extra Magic Hours.
The extra evening magic hours can be killer at such parks as Animal Kingdom. We took advantage of the evening hours at AK and rode Expedition Everest about 10 times in a row with no wait.
Also, late in the evening, around 9-ish, there were no lines or waits for a lot of the attractions in Fantasyland.
We went to Magic Mountain during this time, too, and the only one with a long wait was X2, which by the way felt rougher to me than I remember in '07. Anyway, to ride all the other popular rides the longest wait was maybe 20 minutes, and the park was packed. We arrived at 10:30am and ended up leaving around 3 because we hit everything, and had time to eat in the park.
I think the day of the week factors in, depending on the time of year. More importantly then any of the stuff mentioned above, always give yourself enough days to visit any of the parks so that you don't get frustrated when you are visiting on a busy day.