We were faced with the choice to design the navigation form with our current project. We narrowed it down to the slide menu and the drop down menu formats. I had hesitation with the slide menu as it offers some additional features, however it has some big issues. It typically sits in the upper left corner. Look at any mobile study (Luke W, perhaps) and you'll see the reach zones with users' hands. The right hand hold of the device causes the user to hyperextend their thumb to reach. Additionally, the top left location is sometimes reserved for a Back button in a linear flowing app.
So, we tested the two navigation forms with users in our usability lab. We had 15 users come in and work on multiple devices with various mobile prototypes. We saw a clear case that users preferred a drop down menu located at top right. Users were mostly negative about the location of the left corner slide menu trigger as well as the triple line iconography that typically represents the slide menu button.