Currently using the online platform for ATPL(A) study. I can only compare to CASA CPL theory but so far it has been an excellent experience.
The IPad app is easy to use and the theory content so far has prepared me very well for the exams (in combination with question banks). The BGS theory bank is obviously more UK centric so I have been also using ATPLQ which very closely aligns with EASA exams.
I have attended the revision week online as I work in a European country and can not attend in person. It was well set up and I didn’t feel disadvantaged for not being there in the room. You need to have completed the theory for the module before the revision week and as such they are not about teaching the content but rather highlighting some important areas for the exam and giving useful tips and practice questions to prepare you.
Overall I can recommend them, especially if you are a distance learner.