Richard MacManus of ReadWriteWeb has a great quote from Techmeme founder Gabe Rivera:

press releases are kind of like poorly-written company blog posts

Well said! It's a defense and critique all rolled into one. I'm not convinced that blogs will replace press releases, though I think blogs continue to make PR of all sorts better.

There's been plenty of blogosphere discussion of press releases, e.g. see this wrap-up from PR Blog News in January. One result: an ongoing effort to create a Social Media Release.