From the developers I work with and talk/listen to, pretty much no one uses those resource ID bindings and rather uses something like Butter/KotterKnife. And with findViewById() working without type cast starting from the next version (as mentioned on I/O), even less would see the benefit.
Someone told me, that those resource ID bindings inside the kotling extensions are pretty hacky under the hood (not sure if that’s still the case). And also naming conventions get totally fucked up because you usually name your IDs in snake case in XML but write code in camel case. So you have to either use snake case inside your code or camel case inside XML which I really don’t like.
Just my 2 cents