Dr. Drew is good at what he does. Michael Madsen appears to have gotten his act together. I think Eric Roberts has a chance to do well. Jeff Conaway was hopeless, though, and got kicked out for physically abusing his girlfriend at the clinic. They (of course) reunited in their mutual love for drugs after his eviction from the program.
MacKenzie Phillips was on last season. I think she may have also gotten it together, finally, now that her number one trigger for relapse is dead. She really needs to go back to school and get her degree in something she can use to be a substance abuse counselor. The only way she's going to stay clean for life is if she is invested in helping other people recover.