I've never had a problem cleaning clay pots.
I agree with Fred, cooking in clay doesn't add any special flavor. There's a big difference in flavor, texture and other things depending on the method of cooking, though, boiling, baking, broiling, frying, etc., and the different types of pots can make that happen better or worse. There's something special about chicken baked in a clay Romertopf as compared to baking it uncovered in a roasting pan.
Ceramic pots work great for baked beans, as most would agree, but they aren't required. I saw this molded into the bottom of an old cast iron Dutch oven:
"Baked Beans
1 table spoon mustard
2 teaspoon salt
1/2 cup syrup
1/2 cup sugar
2 lbs beans
1 lb pork
4 onions"
Spence