I like the warmth that drapery/curtains give, but you don't need it on all windows. I feel some rooms need something to frame the window, but not all rooms. I think if you use both is a great idea. You can layer the family room with slat blinds and drapery for a cozy look, and layer the dining room for a formal look. Then just use the slat blinds in the kitchen, powder room and front room of the house for a clean fresh look in these rooms.
Just google layer window drapery with blinds. click Images and you will see photo's of this look. See if it is something you like.
Personally I like roller blinds on remote, with layer curtains.