Thanks for the feedback. I know that my product is better than my competitors; both from an aesthetic and functional point of view. This is the first "real" website I've started that I've run like a proper business.
My primary concern is that the idea up until now has cost me only a few hundred dollars for registrations as my business partner and I have done the coding and UI ourselves. Obviously the next step is the big jump into marketing which isn't going to be cheap.
I'm happy to spend the money on marketing (paper based primarily), however having someone else enter the market in the same space has made me a little nervous about how this could impact me.
We're actually based in Australia, so our market is much smaller than the US market.