What makes advanced dancers look so good?

Physics and comfort. The best dancers have found the most efficient way of moving their bodies. It's all about science. Because they are moving more effieciently, their movement is more ergonomic, more natural, easier to do, and they feel more comfortable. How do they get that? Great instruction, feedback, and practice...and in rare cases, natural talent. Be cautious with your admiration: some dancers look great to the untrained eye, but are an eyesore to trained dancers, or a sore shoulder to their partners.

Why do advanced dancers follow me perfectly, but beginners can't?

10% of the time it will be because the follower's frame is really that bad (or she has not been taught frame yet). The other 90% of the time, it's because of you. Advanced followers are not only advanced at following a true lead, they're also experts at following poor leads, because they can tell what you meant to lead. So they're expert fakers: they can cover for your mistakes. So the dance runs smoother because they appear to follow you better. Beginner followers haven't tuned this skill yet, so a poor lead fails on them more frequently.

How important is the "stretch" thing? Can I get away without doing it?

NO. You can't get away without it. It is the characteristic of WCS - the essence of the dance. Without it you are just walking around holding hands to music. If you think you like WCS now, and you aren't doing stretch yet, you ain't seen nuthin' yet, baby!

Why do most classes teach patterns, yet everyone says to just go with the music?

Most instructors teach patterns in order to "get people moving" or because that's how they learned, so that's how they teach. WCS is a dance that is becoming less and less reliant on set patterns, and more reliant on technique in order to create patterns on the fly. The latter allows you to improvise according to how the music inspires you. So, when you learn patterns in classes, learn the skills, but pay more attention to how movements fit the music. Pay attention to all the technique tips you can get your hands on.

How come the top dancers don't do their triple steps?

West Coast Swing encourages musical interpretation and expression, which sometimes means that there is a more appropriate movement than a triple step for a certain part of the music. Or sometimes, they do a triple rhythm, just not in the traditional 3rd position. Either way, triple steps are a default movement, but not mandatory on every pattern. On the second triple step there is an anchor at the end, but as long as the dancer still does an anchor at the end of count 6 or 8, he or she does not need to do a triple.

"When in doubt, Ripple or Triple" - does this have any merit?

This is a cute piece of "advice" that sounds like it came from a jaded teacher who was disappointed with her lack of competitive success. When in doubt, triple, yes. Because the triple step is the core rhythm of the dance. But ripple? Body ripples were a trend about 6-7 years ago that the Champion dancers started doing and everyone tried to copy them...ad nauseum. Like those songs on the radio that sounded great - until they played it 10-20 times per day! Ripples are like any other styling variation - they should be treated like salt on a meal - a little makes everything better, but a lot can ruin the meal. They are to be used sparingly, and only if you're good at them.