I’m a big fan of graduated ND filters. It just feels good to get the exposure right in camera and GND filters have become my most important piece of equipment besides my camera and tripod over the last years.
I usually use one or two GND filters stacked in front of the lense when I shoot sunrise or sunset scenes and this gives quite good results … mostly.
Sometimes, when the horizon isn’t even enough the filters produce some dark shadows and I loose detail in those areas. Or sometimes when I do a long exposure shoot, changing light conditions during the exposure lead to an image which either is to dark or has some lost highlights in the sky.