Domain Names - An Old Question Re visited

What are your thoughts on the best domain structure.

For example, let's say I want to target "lose weight acai berry"

does it make a difference with the se's if i use hxxp://loseweightacaiberry.com or hxxp://lose-weight-acai-berry.com

Does one version get better results that the other?

Also, would a subdomain configuration work better if the main keyword domains are already taken?

Example: lets say acaiberry.com is taken, would acaiberry.loseweight.com have the same result with the se's?

What are your thoughts and experience?

I believe the only time you should use hyphens is when the keywords could be combined different ways, like expertsexchange, expert sex change, experts exchange. Otherwise google will parse out the words correctly. hyphens also make it harder to speak the domain out loud. experts hyphen exchange dot com.