I have been using Free-Press-Release.com and had some steady flow of visitors coming through to my sites. The problem with press releases is that the traffic will start fast then drop off quickly as it its no longer considered new news. My releases still ranked well in search results though. If you have been able to get traffic from press releases please post below.
Congrats! However, I think you need to provide content for the user to give him/her a reason to return to your site. After the press release, then what? I think, it all depends on the market... What kind of business you're in. I'd say, a generic answer is not possible without more detailed info of your business. I understand if you wish not to share.