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Here's a thread on Editing Press Releases [webmasterworld.com] that you might want to read.
It doesn't matter in the end - PR on your own site shouldn't be targeting your core terms (you do this using unique pages of content) - if anything PR / articles that are distributed would target your brand term and possibly less competitive key phrases - they will never rank well for competitive terms, be it on your site or a hundred others.
Regardless, what is the objective of your press release? Exposure. It's not going to bring direct traffic and it's likely that inbound links from PR / articles are heavily discounted or even completed ignored. It's the buzz - the exposure that your PR creates that benefits you, both in terms of marketing and in terms of SEO.
Edit>> Sorry , I forgot to mention the dupe content question. My first ever press release/article was to introduce my site. It is now on hundreds of other websites/blogs, and so far it hasn't been considered duplicate content.
This can be part of a brand protection exercise or even a damage limitation exercise if you have received bad coverage somewhere that is ranking for your brand terms.
No duplicate content, no supplemental pages, no penalty.
Generally I think the age of the site and how authority it's considered by Google are the main factors for success.
For many of the press releases, if you search for their title on Google you will see our page rank higher than the corporate original's one.
PS. FYI there are no direct backlinks in the press releases that we republish.