The answer varies depending on who you talk to & what you use them for. Some people say they are a complete waste oftime whereas others (like myself), use them almost everyday.
If you plan on blasting out insane offers of incredible riches in 24 hours, I would suggest giving them a miss. You will be lucky to score 1 hit for your trouble.
But if you are just trying to introduce people to what you have & use a compelling, believable headline you will get areasonble click thru rate.
It takes me about half an hour a day to post my message out to about a dozen different lists of various sizes. I don't try to sell anything but introduce my newsletter, so I can then keep in contact with potential customers.
If a headline isn't getting a response, try altering it a little till it does work. Try rotating a few different adsso the same headline isn't seen day after day. Don't be scared to chop & change until you find something that doeswork.
Bottom line is I feel as a free or low cost form of advertising safelists provide an excellent way for newbiesor long time marketers to get their message out there.