For one, I like that I will not have to sprint to one side of the park in the morning to get a fastpass to one attraction, only to have to sprint back to the other side of the park to ride another attraction on standby (eg TT and Soarin, KS and E:E)
Isn't it possible that FP's may only be available at times close to each other? Or, on the other side of the spectrum, maybe FP's will only be available for times WAY spread apart. Not that that differs from FP now. I'm just trying to figure out how the new system will work.