I think cleansing conditioners are worth it depending on your wash cycle.
For example:
They are not worth it to me since I only wash every 2 weeks or so and by the time I get to it, I'd much rather just use shampoo to ensure a super clean slate.
However, I use a cleansing conditioner in my son's hair. I wash his hair on average every 3 days so I don't want to strip it every time by using shampoo. I love Curl Junkie Daily Fix. It removes enough dirt and sweat without leaving his hair dry. You only need a little to make it work too. I just replaced a bottle after using the last one for 2 years. Plus it doesn't burn should it get in his eyes. Win! I still wash his hair with shampoo but only after he gets a haircut (every 2-3 weeks) so a cleansing conditioner is not his only source of cleansing but it is his main source.