Yeah I used to use the granny gear some, but I told myself to not do it anymore. So now I try and keep it in the big ring unless I am climbing then I go to the middle. Trying to get my leg strength up. Some of the hills I always did the granny gear and easy in back, I now am in the middle cog about about midway in the back.
My only flaw with doubles is that it really cuts down on yours gears. I have a 9 speed in the back. So with a double it will almost take out about 11 or so gears since I won't be able to use the two extremes because of cross-chaining