Again, you can use HipChat and get something closer to the best of both worlds; drag-and-drop file sharing with a standard (well… more standard-ish) OS X interface. It's great for you that look-and-feel isn't so important to you, but it is to a lot of people, and that includes myself.

At any rate, on Slack, I once drag-and-dropped a text file with the output of a shell script that a colleague wanted to see. He started telling me how it was strange that the output seemed to cut off right in the middle of a line. lol, just kidding, Slack was just cutting it off like that, since Slack apparently can't show more than the first few K of a text file for some reason SO WHY IS IT SHOWING IT AT ALL ARGH