Although some of the testers weren't exactly in the "target market", by having some people that weren't designers or developers muddle through our demo, we were able to fix some really critical bugs.
I even met some people through the service (testers) that were willing to jump on Skype with me to discuss the product and who were interested in taking the beta process further.
I'd highly recommend you try them out. The social strategy Ross is going for here may be a little misguided, but the product itself, and indeed Ross (as far as I've dealt with him) are hard to fault.