In the reality you should take the time when your traffic is small to reach out to customers and get early feedback and polish the product as much as possible. The more work you put into based on real feedback from real users before the numbers get big, the greater the quality of the first impressions as your target audience trickles in.
Once your product is good enough, there are many ways to get users in. Press is one of them, but in my experience it comes on its own and is not worth putting much time in compared to more targeted user acquisition. In general, word of mouth will always always be the best, and that takes a great product.
I'm not even talking about the conversion rates and the quality that HN brings over TC/Mashable.