Bought it to plug my midi keyboard, midi controller and hard drive into, and left my free USB port on my MacBook Pro for my audio interface. Works perfectly and had no issues. I also use it to connect my to CDJ 900s and my DJM 850 mixer to my laptop and it works perfectly. I use the external power source for both of these.
Really good quality and very easy to use. If, like myself, you plug it in and cannot put files on it or have to use the software included with it then (on a mac) simply go to disk utility in applications and go to the name of the hard drive and then just go to erase and click format and ta-da! A simple drag and drop hard drive is there.