I have been a user of the paid edition for a while and have encountered some quirks and annoying issues.
* The Boxcryptor folder is not acting like a real folder, e.g. you can't view an image and use the Photos app to flip through the images, you have to click on them one by one in explorer
* When viewing a folder with a lot of images it takes a long time before all files has been enumerated and sorted correctly
* On two occasions I've experienced that boxcryptor would upload unencrypted files, even though I pasted files into a subfolder in a folder that was set to be encrypted - accessing onedrive through a browser confirmed that the files where plaintext :(
* Frequently the app is very slow at uploading pictures. I even configured it to upload "Instant"
* A peculiar thing is that on my last vacation I could rarely make boxcryptor upload images even if I was connected to the hotel wifi (which admittedly was slow, but worked and occasionally allowed even Netflix streaming)
* Most of the uploading resumed when we came home and connected to our own wifi
* One days worth of pictures were never uploaded, that day we were in a mine and had no connection whatsoever, however, boxcryptor uploaded pictures from previous and later days when we came home. How can one trust boxcryptor to upload all files, what other files did it not upload, which I didn't notice yet?
* When opening the app it is frequently so slow, that Android prompts you to close the app or wait
Given the sync issues I would love to see a "resync" feature for media files.
I have to admit that while I am happy with the core features of boxcryptor, then I am actively searching for alternatives, because of the above nuisances and will proceed with another solution next year if I don't see improvements soon.