Take my, and everyone's advice, with a grain of salt. Few people have experienced enough launches to offer a very objective view of the patterns, so you're going to have to make the decision for yourself.
As a rule of thumb, from the launches I've seen and been close to, they are not make-or-break for a company/product. You might get a bit of buzz, you might have a TC or RWW article about you, but as I think of successful startups that I didn't personally know, I can remember only a few launch days.
The important factor is in one of two categories:
1) consumer app: the app produces a TON of value, and everyone tells the people they know (viral growth)
2) business app: viral growth is a factor, but there's probably going to be a lot of sales-y activity required.
Neither of these categories are largely dependent on a launch. A launch is more important when you've already got a ton of eyeballs.
Again, this is a rule of thumb, and I'm not aware of a single person who I would say is a true expert around launches.
What do you think?