I used to be a big slow cooker proponent but I've been using it less since I've discovered the miracle of cast iron dutch ovens. For things like pot roasts where browning is key, I've gotten much better results out of a dutch oven than the slow cooker. Yeah you can sear/brown the meet before putting it in the slow cooker, but the browning effect continues in a dutch oven to an appreciable degree while it cooks in the oven.
Where browning isn't really needed, then the slow cooker is great. I'm thinking shredded taco chicken, throw it in there with some onions, peppers, spices, an anchovy (important!) and a little beer and you've got something delicious. Does great for soups too.