Dropbox, why are you ruining Mailbox?
First development stopped for several months, then an ugly and buggy version was released, then the design was reverted back to the original one, but all the bugs and instability remained there. On El Captain, the application is just not usable, and the OS has been available for developers for almost 6 months now.
The apps may be free, but I think they owe their users an explanation. They've been very vocal on Facebook, by email, on the support forums, etc. Dropbox/Mailbox have remained silent. Their last Facebook post date back to June, and their last blog post to April.
I love Mailbox on the iPhone and the iPad, but it's useless if I can't use all the great features it offers on my desktop.