Entirely swear by mine. The trick really is not to take the lid off however tempted you are to prod around. It breaks the moisture seal that forms between the lid and the crock - same effect as leaving the door open on the freezer.
You can slow cook chicken without any liquid at all and its so succulent. Bush the bird with olive oil, season with salt, pepper and paprika, bung a halved lemon inside (and fresh bouquet garni if you want) then sit it in the cooker on four walnut-sized balls of crumpled foil. Less than five minutes prep time, stick it on low for and get on with life for 8-10 hours.
They also make a really good classic bolognese sauce. Hugh Fearnley-Eatsitall has a solid recipie; once you've done all the meat and veg browning, add your liquids and cook on low 6-8 hours.