There comes a time in every serious adventure onto the web that you have to consider your hosting options. The free services aren't enough (you're using too muc bandwidth for example), shared hosting means you're open to the problems, spikes in traffic, even denial of service attacks on those you share the host with.
So, as traffic grows you'll need to look at a dedicated hosting solution and DMG Dedicated Servers looks like an extremely good place to get one.
They've grasped the two most important things about the business. The first, that it is their customers that make of break a business, so they must be treated as the most valuable asset. The second is that it is uptime that is most important, which is why they use AT&T as their primary provider.
Very much worth checking out if you need to upgrade from your current hosting solution.