Hi Ken!
I like the last 2 videos the best... those guys seem to project more enthusiasm than the others, and their responses seem more natural.
I know nothing about the topic, so I'm not sure about the
content of their comments. Will visitors to your site be familiar with the terms they use? (What do candles have to do with trading stocks?

)
Suggestions for future:
(1) Technical stuff: Find a separate room. There's too much distracting background noise (perhaps it can be edited out?). Better lighting is needed.
(2) Have someone NOT connected with the seminar ask the questions. Most of the responses seemed forced... like they were more interested in pleasing YOU than giving honest opinions. I know that's probably not the reality, but that's the perception I got. Perhaps if they were talking about the seminar to someone they'd never met, someone who approached them with "I'm thinking about signing up for this... do you think it's worth it?" type questions, their responses may be more "real."
Here's another "out of he box" thought... Maybe your interviewer could pretend to be an investigative reporter who's looking into seminars that rip people off. Have you ever noticed how people respond in discussion forums to insults and negative remarks about products they've bought? They become RABID FANS, coming to the RESCUE of someone they admire and respect, and raving about the product they are fully committed to. Those comments are much more emotion and more POWERFUL, usually, than the average testimonial... don't you think? Of course, after the interviews are done you could reveal the subterfuge.
