No, I wouldn't recommend this. It'll cost you anywhere from a few thousand to 10k+ per month. There are much better ways for you to "get the word out".
PR agencies are what corporate managers hire to justify their marketing budgets. You're a startup. Be scrappy. Be creative. Think outside the box. You'll come up with ideas and ways to market far far more effective for your market than most PR agencies.
Noticed that Mint hired a PR person very, very early and it worked out pretty well for them.
It also depends on the type of business that you're building.
No. You can do a much better job yourself
Thanks for the input...very much.
Maybe if you've already burned bridges and ruined your brand.