My mum cooks chicken curry in a slow cooker, I think mostly for convenience as we're both out for about 12 hours during the day. It's delish!
Think a slow cooker is all about convenience. I've done curries in one and they have turned out great. Never do them any longer than 5 hours though. It's just sometimes nice to come home, open the door, and know that dinner is done. Bung in a Uncle Ben's 90 minute rice pkt and eat. For working moms and dad's, and for people who like to spend their free time not in the kitchen, slow cookers are ideal.