The two main improvements seem to be:
- Improved compter player AI (especially with regard to property transfer)
- Support for international maps (so American players can rename what we call "Trafalgar Square" to the more familiar "Illinois Avenue")
There are also numerous bugfixes and cosmetic improvements, such as ownership 'flags' displayed on the board to show who owns each propery. You can download version 2.06 from Duncan Mortimer's website, or right here from Acorn Arcade.