This thread appeared recently on the Seattle Tech Startups (STS) and occurred around the same time as this approach by Jason Calacanis began to get some coverage.  While I think Jason's approach is creative and agree with some of it, there are still some hard truths about building market awareness.  PR firms are only as good as the material, market, and people they work with.  That said, I have had too many poor experiences with bad PR firms including both local boutique shops as well as national/global players.  Local players can be clueless about the national or international stage and big players will sell with seniority and then staff you with a freshly minted college grad as your day-to-day contact. 

If you expect your business to soar by blindly hiring a PR firm, you will be disappointed.

Here's my response to the thread about company launches on STS:

Identify the issues that are core to the problem you are solving and own them. Add something to the discussion about the problem you are solving and back it up with your expertise, customer value realized or even survey results.  Stats will get you coverage.  Also, building a coverage pipeline is like building a sales pipeline.  Lots of activity to get the results you desire.

PR can have a good ROI if the firm you work with gets it and makes themselves accountable to hard metrics.  Your job is to give them something to work with and view building market awareness in the broader context of growing a company.  If you are in the market, I strongly recommend VisitechPR out of Denver. I have worked with them in my last two companies and can't say enough great things about them.