What are y'all's experience and opinions on internal engine coatings?

I'm talking specific things like:
thermal barrier coatings
thermal barrier head coatings
low friction piston skirt coatings
low friction bearing coatings

Are there any of those that are not really worth it? I.e. really low return on $$ invested?

Is www.swaintech.com the best? They seem to be the most popular but that's not always the best.