This is a great system... there is however a problem. When you start a new import, it truncate sthe existing xf_import_log with a function called "resetImportLog". I do understand why this reset is important; if an administrator wanted to import data from multiple forums into a single forum, the reset would prevent ID clashes.
However, at the same time, I would like there to be an option to skip this reset; in debug mode only if so required. Why? Because sometimes the information in a previous import is important for a subsequent import... such as user ID information.