I am not sure if someone on this forum already shared their results with press release. But here it goes:
I submitted a press release to WebWire (WebPost) three months ago. My goal was to increase seo traffic to my website. Right after submission, there were some web syndications growing steadily (number of raw backlinks grew). Eventually, it grew up to thousands web syndications. I got up to about 10-20 visitors per day. Then backlinks started to drop off slowly over time. Currently I am down to 40 web syndications and about 0-3 visitors per day. I guess press release is good for temporary traffic boost. Dunno if its worth the investment for longer term.
Hope you can share with your press release results in a long term (not just few weeks).
All the best!