I've seen 2 or 3 episodes, and I thought they were well done.

I've watched almost every episode of this since I discovered it partway through the last season.  I missed the last few because I've been too busy.  I think Intervention is an excellent show and really drives home the sadness of drug addiction, and the meaning and effectiveness of an intervention at getting people to seek help.

The only problem I have is that most of these people relapse.  An intervention is 90% successful in getting them to get help - but that help only works in 15% of their cases.

I also like how the show really shows that drug addiction is often a family/peer problem, and that the person afflicted is just the "tip of the iceberg" - the part that shows the deeper family problem.