Sex is a learning experience... the more you learn.. the better it is.
So, yes, not only do I tell them that I enjoyed it... but I mentioned specifically what I liked, and make suggestions about what else we should 'practice.' It's suppose to be fun and much better when mutually enjoyed.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen