Answers.
- Do you find /x regexes easier to read/understand, or harder?
In the real world? Generally harder. But some complex/tricky ones benefit.
- Does this "ease of reading" change one way or the other as you gain experience with regexes?
Yes. When you don't understand them, the comments can help. They are a great learning tool for explaining how an RE works. But they are a crutch, and like real crutches, they bang your legs when time comes to start running.
- What kinds of rules should be followed when using /x to ensure the best readability?
My rule is that if I feel tempted to use /x, then that is a sign I need to refactor my problem. Instead of single massive regexes, I like to have straightforward regexes together with higher-level looping logic. For this pos is quite useful to know about.
Summary: I think /x is a wonderful idea, which I am very glad exists and is excellent for teaching. (Indeed the inspiration came from trying to teach someone.) But using it in production code violates the rule of trying to only maintain one document. If you can read the RE directly, then the comments are superfluous at best, and misleading at worst.
For anyone who doesn't believe that comments in the wrong place can be misleading, I invite you to read Things are not what they seem like. again. And this isn't just a bizaare obfuscation technique, in the real world overly verbose commenting is a very common way for well-meaning people to produce unmaintainable messes...