Not at all. There's a risk. Sometime they will sell your domain name to some third party if they get a higher bid. It's really painful, when they do it after we create quite a big visitors to ur domain name.
well, they are quite useful, but people dont preffer many of them. Its something that 70% people think its free but only some of them know it can be registered and its not only the redirection service. I would better stay a bit off it.