A lot of effort has been put into the import of various file formats. However, please bear in mind that imports are best-effort. Except for STarKos (SKS) and Arkos Tracker 1 which formats are quite analogue to the one of AT2, each music software has its capabilities and design, which make it sometimes very difficult to translate into another tracker.
Import is not made to get any of your <enter your decrepit tracker here> song and use the AT2 players: you will probably have to make some adjustments. If some features are really missing, please contact me (by mail or via the forum) and I will see what I can do. But import is mostly useful for musicians wanting to finish their song with AT2, and make a switch to AT2. Please don’t look back to your previous software :).