The main changes I've done are:
- Polygons representing one country/area are merged into one feature.
- Added ISO 3611-1 Country codes (alpha-2, alpha-3, numeric-3).
- Various feature changes to make the dataset more compatible with ISO 3611-1.
- Added region and sub-region codes from UN Statistical Division.
- Added longitude/latitude values for each country.
More information on this page and in the "readme.txt" file provided with the dataset. You can download the the dataset in two resolutions. I recommend the simplified version for thematic web mapping.
The dataset could be further optimised by removing small island polygons that are not individual countries.