I've posted to both free and paid sites as many have done here. I'm going to be posting my first release for my own business and I'll do the same both free and paid.
I find that the free ones do offer good
SEO and search opportunities for those releases posted there. I don't see them landing in the laps of the editor's desk of the local newspaper, though. Those seem to be the paid ones, however, if I send a release to my local newsletter(s), it is still "free" if it is picked up as a story.
It pays to be persistent, to post to as many releases as you can free and paid, if of course the latter is in your budget. There are $80 per posting sites and those that are more expensive but allow for at least one releases submitted per week...depends on your budget and time you can spend writing them.
Diana Ennen's interview
here on VAF is wonderful. I've taken
PR classes online and she's been a co-presenter with additional helpful advice on release info. It's well worth reading and bookmarking, as I have done.
Best Wishes.
Jan