Apple turned the launch of the iPhone 3G into an event, but the first day was marred by the fact that credit checks are individual and don't benefit from economies of scale. There was lots of publicity but also considerable unhappiness.
In an age of always in beta, it surprises me how many companies still focus on launch days and events and risk anti-climax as a result of being unable to service the instant demand they've generated.
Even if day one goes fabulously, you're going to have cumulatively more customers to deal with on day two and beyond, so why this obsession with hitting a home run on day one? It's not how you built your business, so why change a successful formula?