We've never used a PR person or firm and only one time did one of us email a reporter out of the blue.
We are in the "lucky stiffs" category. ;-) Reporters love the information overload / productivity stuff and we tend to have lots of great data that excites reporters. We've done a few things to encourage this (blog post here and there), but for the most part, it's totally inbound.
In terms of signups, we've never noticed a huge bump in signups from mainstream media (a few national tech radio shows, NYT article, etc). We get more signups from blogs we've never heard of. It's great for SEO and credibility, tho.
