Have been waiting for an import plugin like this for a long time. Simple design but powerful at the same time. Since it hasn't been long released, initial development changes show rapid improvements.
One feature request that I personally think is essential is pre-filled table detection. E.g. Mapping and importing a csv file multiple times results in duplicate tables/duplicate posts. If the plugin had the ability to detect if a table has already been mapped previously, then skipping it if that tables content hasn't changed, updating the table if content has changed. Also being able to map additional tables to previously mapped tables.
I tried importing a csv file from Magento wich contained 170 eccommerce products and 25+ tables. Selecting the tables I thought I needed, only to realise I missed an important table and had to remove some formatting on another.
I corrected my initial mistakes and tried a second time. Rather than updating my first import tables, it created another whole set of posts. Once thats integrated as a feature. Will be the greatest plugin.
Keep up the good work.