I have a Rival Crock-Pot that comes with a few different heat settings. It comes with two high heat settings, which run for either four hours or six hours, and two low heat settings, which run for either eight hours or 10 hours.
These might seem like enough settings to make slow cooking a snap. However, I found that many recipes called for either four or two hours on low, which meant I had to be home to switch my slow cooker to the "warm" setting.
I've been told by multiple slow cooker lovers, cookbook authors, and chefs that the best part about using a slow cooker is being able to set it in the morning and have it ready by the time you get home from work. However, depending on your recipe's cooking time, that may not be possible.