A good PR firm works to maintain a very personal and trusting relationship with major news outlets, including the popular blogs and web presences. While there are a lot of bad PR firms out there you should avoid, a good firm is extremely valuable and should be included in your marketing strategy once the product has shown life.
However, most likely your first year (or two) you'll be able to handle a fair amount of the basic PR work yourself. Here's a good blog post from Josh Dilworth who works with a lot of tech startups.
We just had a discussion on PR firms that pretty much settles it in my opinion (http://news.ycombinator.com/item?id=462493). How can I include it in this thread? Hyperlinks are just not as efficient as some cute Ajax inlining...
However, most likely your first year (or two) you'll be able to handle a fair amount of the basic PR work yourself. Here's a good blog post from Josh Dilworth who works with a lot of tech startups.
http://joshdilworth.com/post/68998214/what-the-heck-is-pr-an...