The main problem with slow cookers are that the liquid is not reduced properly which have to be done as a separate step using an ordinary sauce pan.
If you do a 7-hour lamb in a pot in an oven, you have the opposite problem, as it's a bit warmer, and might have to glue together the lid with dough. I think the taste will be better though, as I think there is more caramelisation going on at higher temperatures.
