The script will likely present the greatest challenge. It is Arabic but nevertheless it is an alphabet. Beyond the letter forms, you will need to adjust to the idea of positional capitalization and joins.

Farsi/Persian also has a fairly complete coverage of various sounds, some of which may present a problem to the non-native speaker.

Finally, Iranians do have a fairly distinct partition between formal (written/official) language and the everyday conversational usage. The conversational style is much more fluid.