The software works well despite a few bugs that can sometimes make you lose unsaved data. So remember to save regularly! To close a document with unsaved data, do not use the dropdown menu and tuxguitar "tuxguitar leave" the program will close without saving your data. Click the close icon and it asks if you want to save your changes.
I've had several myself and I'm pretty satisfied. It is a good alternative to Guitar pro if you do not want to spend 50 euros.