My new favorite Cookbook is Secrets of Slow Cooking, and I've learned so much about that 'old' appliance! They recommend having two sizes of cookers, since they need to be at least 1/2 to 2/3 full to work properly. Since it's just the two of us, our big Rival 6 qt oval isn't needed half the time. We have Dave's old round Rival that we use for smaller jobs, and we notice that the food doesn't dry out or cook too long when we use the right size cooker for the job.
Our Rival isn't programmable, but Dave turned it into a high-tech machine for me. He plugs the slowcooker into a regular timer like you'd use on your lamps and sets it to go on and off at scheduled times, and it works perfectly!
~ "The right shoe can change your life...."- Cinderella ~