Depends on what you mean by "worth it."
I mean, if you're going to be writing a press release anyway, why not submit to a few free sites in addition to at least one paid distribution channel... especially considering the only thing it costs you to submit to the free sites is a minute of your time for each. (But I wouldn't spend much more than that on it!)
On the other hand, I wouldn't bother specifically writing a press release just to submit it only to free services. If what you have to say isn't "newsworthy" enough to warrant paying a few bucks to get the word out, it probably isn't newsworthy enough to warrant spending the time to write the press release in the first place.
As to whether they're successful in terms of driving traffic, my general experience has been that press releases themselves are not particularly effective as traffic generators.
When those releases get picked up by a media outlet or two --
that's when they start generating traffic. But frankly there aren't that many people who simply troll press release sites, visiting the websites of the companies they find therein. That "pickup" is the key.
Which then comes back to the newsworthiness of your "news." If you've got something truly interesting, such that it gets picked up by blogs, websites or other media outlets, that can go a long way toward driving traffic. But if there's nothing interesting or "newsy" about it, it doesn't matter how much you pay for the distribution -- if nobody picks it up, it isn't going to get you anywhere.
--Torka
Web Press Releases
