Downtown Host gets "lost" in the mix many times, but they are a provider with a solid track record. I definitely consider them a premium provider.
As I mentioned in another thread, Hostgator has it's share of supporters, but more than it's fair share of detractors. With Hostgator, you'll typically be fine if you use basic/"normal" resources, but once you go outside of their expectations you will run into problems. This is the big drawback with companies that offer "unlimited" plans as they are never truly unlimited. Hostgator (as with any other similar provider) has internal limits set that WILL be triggered at some point, you just don't know when. Plus, "unlimited" typically means oversold, which can lead to performance problems. Even though it sounds backwards, if you expect your site to continue growing, I'd go with a non-unlimited provider so you know exactly what to expect. Choose quality over quantity when it comes to a host provider...it's the core of your business.