Import for K2 is still at an early stage of development, but is already working well.
It allowed me to import and/or update tons of data into K2 in a snap. It links articles to any category, wherever this one is located in the hierarchy.
Import for K2 still lacks of an "import mask", where a user could save his configurations once for all. Same work has to be done over and over, and can lead to mistakes.
Communication with Artur (the developer) is great. He's willing to develop his product, helping and listening.
The price he's asking is ridiculous, and he's open to collaboration.
Having reviewed the market, Import for K2 is the only product enabling to import csv (Excel exports) tables into K2 and linking them to K2 categories.
I hope to find enough time to keep participating to its development through further testing.
Thanks to Artur for his contribution.