This site is very genuin and if you are not on it, you are missing a lot on great free traffic from Twitter. It's perfectly in terms with Twitter's TOS. Added to this is http://easyretweet.com which is also highly recommended if you want more free traffic.
I went and looked at this site. It is too fishy for me. There is no real information about them. There is no faq section. It is set up to have peope believe they are part of twitter. You don't need this site to Tweet your blog, hub, other sites and blogs. You can do it right from those sites. Either way, you need a Twitter account. There was another automatic Twitter program going around which was against Twitter TOS.
This one is probably a Tweeter TOS violation. Twitter has a retweet function right on Twitter.