Totally agree homerbart....i've stopped using mine now especially for chicken and pork. I might do a bit of beef or lamb in there occasionally but that's it.
I suppose it would be good for stuff like mutton....particularly a mutton curry or stew done in the slow cooker.
Trial and error with timings really, but starting with a cheaper/tougher cut of meat would help. I don't like it when the meat goes all sinewy and breaks up too easily, after too much cooking, so I keep slicing bits off to check how it's going. Try a brisket pot roast, you may change your mind. Also I usually cook on high for an hour or two and then low for the remainder.