I use this once a month in conjunction with the Extreme shampoo & daily conditioner (which i use every 3rd wash). My highlighted hair is damaged but not overly so, so I don't need to overdo the protein element.
I wash with extreme s&c, towel dry, spray with CAT and leave in for 10 mins and rinse. I do follow with Redken's Smooth Down Butter Treat under a hot towel for 20mins as I do find it quite drying. The CAT (with the s&c routine) adds the missing strength and the butter treat adds the gloss, moisture and manageability back in. It's a winning combination and because I use it about once every 3 weeks it is pretty economical cost-wise.
I would give it 5 lippies but I do find that my (normally very easy-going) scalp is a little irritated by the proteins in it, it's not too much of a problem because I use this treatment so infrequently. It might cause a problem if I used it more regularly and the proteins built up though.