Google says press releases including anchor text do not help search rank. While not all press releases are spam, pr web, business news wire, etc will allow you to put what ever links you would like. As such, this is a spam. Anchor text and keyword stuffed releases offer no value.
Some press releases are pertinent. These include industry awards, announcements, and other things shareholders and customers need to know.
It really depends on the website where these scenarios link. If the target does not have a portfolio of spammy inbound links and the press release is not spammy, it may work.
However, you cannot use a press release as a single strategy. It may support an existing quality link portfolio.
At the end of the day a press release is not different than an article directory. This is not trusted content.
If a press release happens to get syndicated and picked up by other news sites and the anchor text remains, then there may be an upside, but this is rare.
Now, if you are using these services it is critical that the press release also reside on the site as well. On the version of the release on your own site you should make sure to interlink key words to other parts of the site. The press release can be a good navigation tool. This version of the release is likely more trusted that the public releases pushed out by third parties.
The degree of usefulness of a press release is debatable. But, used appropriately they can be considered a part of the strategy.
