I love my slow cooker, so if you are thinking of getting one, go for it.
As for thickening, sometimes things will thicken in them. If you want something nice and thick i usually take the lid off for the last 30/ 60 mins to help it thicken. However one of the best thickeners is pearl barley or dried split pea's etc, these are really healthy, are free, and really filiing and tasty.