Depending on what you are trying to run CJ could be the best and for some offers possibly the only place you could be. They have a lot of name brand offers you won't find anywhere else. Also, they have a lot of options for advertisers that you won't find on lots of common CPA networks such as high % revshare instead of per lead only and etc. Not to mention the amount of data feeds for plenty of products.
On the other hand, for a lot of the more common offers that you see mentioned on this board you may better off with one of a handful of other networks. Especially if fast payment terms are the most important thing for you. The last point is really why CJ isn't one of the most popular networks around here.