Mine has been negative. Unless you are familiar with the merchant you want to promote, it's dicey. You may find yourself owed lots of money with no prospect of ever seeing it. On the other hand, I am sure there are some reputable programs. Asking about the specific merchant may be more informative.
I have been paid by ClixGalore, but I don't use it that much. The main reasons why I don't use it that much is because I don't like hardly anything about it. I think the way that they show their stats and pay their affiliates is totally wrong and some of their datafeeds don't seem to work properly and are messed up.