Our company has recently been recommended with Recommended Agency Register. I would say it is quite useful for design agencies like mine, as it makes the pitching process much easier and less time consuming. I hope that helps!
Our Agency has been recently awarded Recommended agency status and frankly its been great. although i'm yet to get a direct benefit from the site which is very confusing. The link back from their site and use of logo have been worth the expense. They do need to be more clear as to how the site can be used to generate new business which currently seems only to be a closed access directory.
I think people are generally suspicious of this kind of thing so would be very wary indeed of becoming professionally associated with it until I'd thoroughly checked it out and satisfied myself that it actually had any genuine value (for me) and meaning (for my clients). In short, if people don't feel that it provides authentic and meaningful recommendation (and, as I say, I think most people will be sceptical)then as far as they're concerned you're trying to mislead them.