Quite some time ago, I sold two stories to e-zines. The 'zines stated in their submission guidelines that they paid authors for their work, but I never got a penny. My polite queries about payment went unanswered.
I'm not posting this just to whine (I DO feel better now, thank you), but rather to make a point. As Betsy said in her earlier post, it's sometimes hard to judge the quality of digital magazines. Authors get important services from websites like Duotrope and The Black Hole, but you can never be certain about a magazine's reputation.
Eventually, magazine reputations spread by word of mouth (or word of blog). When fellow writers ask me for suggestions about where to submit their work, I tell them about the 'zines that paid me promptly—and those that didn't.