I haven't used opti-coat for a number of reasons. Detailers who use other coatings have told me that it doesn't have the surface clarity that other coatings have. It is also said to be much more difficult to apply which means higher risk of rescratching the surface. The permanent claim and warranty deter me from using it especially if I, the detailer, am responsible for this warranty even on vehicles that I haven't detailed myself. I highly doubt OPT will reimburse me the cost of my work.
However, it is quite a popular coating among consumers. Whatever the reasons are behind that doesn't attract me any more to use it.
These are just my personal opinions and reasons for not using it.