"Sometimes"?

I've been using cloudapp for the last year, but I'm curious about the dropbox thing.

There's also Servus (https://servus.io/) which is pretty much like cloudapp/droplr but using your dropbox.

Slingshot's supported Retina since V2. Dropbox's auto-upload of screen shots is pretty good (they're using a private API to copy the link the your clipboard before the upload even starts, so it feels really fast), but if you share files outside of screen shots, Slingshot might still fill a need with file and clipboard sharing.