I got a slow cooker about a year ago, I don't love it for everything but it is so convenient. It has taken some time for me to adjust to the differences in using the slow cooker v a pot on the stove, i.e.: less liquid, more herbs/spices.
I make a big batch of oatmeal once every two or three weeks, it's a great overnight dish. You have to use the steel cut oats, and I'd say if you're following the guidelines from a recipe, use only 2/3 of the amount of liquid called for.
We eat beans regularly(spanish/caribbean style), and the slow cooker has been great for this purpose. Throw in a big hunk of calabaza (if you don't have a spanish market, I think butternut squash is the closest, though acorn squash also works) when you start them, it both sweetens them and thickens the sauce. Remember to soak the beans overnight first, this still makes a difference!
I don't love the slow cooker for lentils, they cook much faster than other beans, so for me that's been a no.
Last week I made an easy minestrone--Veg broth and water (3:1 ratio), diced onion/carrots/celery, 1 can diced tomatoes, 1 can fire roasted tomatoes, 1 can cannellini beans, drained, 2 bay leaves, thyme, oregano, 1 hunk of parmesan rind. Cook on low 6-8 hours, then add 1 good sized zucchini (diced), 8 oz baby spinach (if you're using regular spinach, chop it), and 1 1/2 cups small pasta (ditalini, small elbows), salt and pepper, cook another 30 minutes or so, until pasta is done but not mushy. If you're using smaller pasta (pastina, acina de pepe) add it about 15 minutes after the zucchini and spinach. (obv, remove the bay leaves and parm rind before serving)
We've also been using it to prep dried chick peas for hummus. Really delicious, much better than using canned, believe it or not.