That's a nice solution, indeed. I love that it appears to do per-file encryption so that you can download individual files without having to do the whole volume at once.
However, aside from that, it is worth noting that you can get all the features of the paid version of Boxcryptor, and more, for free with TrueCrypt. It might not be quite so elegant in terms of working with cloud storage providers, but it's just as effective at protecting your data and it will let you protect as much of your data as you want for free.
The only other very notable restriction in TrueCrypt vs. Boxcryptor is that there's no official app for mobile devices. However, since TrueCrypt is open source, it's very possible (likely that it's already happened, even - I'm just too lazy to look right now) that someone could write their own compatible app.