Your launch will have very little to do with your startup's eventual success and you probably spend way too much time worrying about it.
That being said, a successful launch can be used to gain thousands of early users if you did your job right when they show up. It won't make or break your startup, but it will help.
In my experience, pitching as a founder is easier than it seems. Tech writers are more friendly than they may seem at a distance - they're only unfriendly to some particularly annoying PR people and, well, fakes. When in doubt, try contacting them, you may be surprised by how open they are to hearing your pitch. And don't forget to follow up.
The problem, of course, as Vinicius points out, is that successful coverage by even the largest tech sites will not make or break your business - it's a nice bonus, nothing more.