I recently did a press release a few days ago and the traffic tripled for about 3 days then died off. This is about normal to any press release I have done. The current press release has 9,000+ indexes in Google and pretty much what was mentioned on that blog post I have done already.
I find unless a press release is actually newsworthy it will not stick for very long. The stats from PR
Web that I get in my email state : Your press release that went live on January 27, 2012 So far your release has received 100732 impressions and 3213 reads