Yes, they are. Sometimes you receive more quotes than you know what to do with! I always look at details; who has answered exactly what I have requested. If I want air fare broken out and they give it to me as a total including the cruise, I am not impressed. This is completely anonymous with no committment, unless someone knows you by your internet name.
We used this site a few years ago, and received almost 2 dozen e-mails from TAs. A lot of them told us to call them to get the best price, review cabin selections, etc. Some of the agencies seemed small, and others were larger and better known. We eliminated everyone who didn't have an address, a well-known cruise-site affiliation or who didn't provide pricing.
Of the ones that actually responded with prices, one (with Cruise.Com) was significantly less. We got information from her on cabin upgrades, since the price she quoted was the cheapest available. We then booked with her, and were very satisfied. That year we also booked a cruise through our local TA to try to support local industry, and were disappointed -- we paid a premium to our local agent, but found that they made very poor cabin and airfare recommendations. I understand that this was only one agency, and other agencies probably provide great service. My point is that once you find someone who's good and reliable, you might want to give them your repeat business.
We book 2 cabins on 2 cruises every year. We've continued to check prices at the usual sites -- then we go back to our Cruise.Com agent, and she's always been able to give us better prices (sometimes only by a few dollars, but that's o.k.) Since we now trust her so much, we find we're checking fewer prices before we say "It's time to call Vicki!." True, she's in another state and we don't get a bottle of champagne or other extras when we book with her -- but we figure that she's already given us a price break out of her commissions. Since we found our Cruise Agent by using this site, we highly recommend the board