As someone said: "There is no BEST host, there are only hosts that fit your needs the better."
And in that game, the clearest your informations will be the better you'll have chance to attract new customers.
By the past, we signed up with many of these directories, to generate traffic and get advantage fom a cheap advertising.
Even if it was hard to believe, the traffic we got from these directories was untargeted and unefficiant. The only good point of these directories was the link-backs to get a better position in SERP's.
We are now more focusing on an extremly targeted audience and SEO.
Since last monday, we hired someone who'll be in charge of optimizing our website: SEO if the way we choosed to follow.
No matter which directories you'll sign up with, referrals links or "customers" reviewed, the traffic you'll get from them will be mainly (i mean above 80%) customers who are looking for the cheapest offers. In facts, only 4% of these visitors will consider reliability, uptime and support.
We can't affoard to enter in competition with providers able to pay $25 and more for a click (PPC) or those who are offering "unlimited" packages for a monthly buck.
That's why we choosed to optimize our pages in a way they will talk to customers who are looking for reliability, uptime, features and support. We will certainly generate less traffic. We are now focusing on quality of our traffic and not anymore of quantity.
So, my tip is: You may sign up with directories, no matter which one, but (and, above all, if you are new into this business) don't expect to get a good traffic from them if you are not able to inject there a big advertising budget (ironicly, which can be used anywhere else, i am thinking about Overture or Adwords, efficiently.)