Is it possible for you to share the algorithm you use to do reverse geocoding (from lat/lon -> country)? I don't see enought data on the downloadable database to do so...
There are a lot of things not included in the download as they are available elsewhere. We focus on offering webservice around the data to save our users the trouble to download and install this data.
The lat/lng -> country reverse geocoding is using country border shape files. The algorithm is just a simple database lookup with postgres.
We are actually working to improve this geocoding service. We have far better shape files than the ones we currently use, but unfortunately without any country information.