ReineD,
When we cross-dressers say things like "feeling like a woman" it is probably due to a lack of a proper vocabulary to sum up how cross-dressing truly makes us feel. I would say for most of us any other experience doesn't compare. One gets a unique wonderful experience wearing women's clothing. The feeling is alien and is completely caused by feminine things ergo it is simple to believe this is how it feels to be a woman. Or at least describe it as such. After repeating it many time many of us probably do believe this must be what women feels like. But you are right there is no way for a cross-dresser to truly know what being a woman really feels like.