Importance of E-Steps

The picture above shows some sagging and some bumps from where the infill seems to be overlapping the perimeter. Fixing the issue involved calibrating/reducing the E-steps (how much the stepper motor moves when it extrudes/retracts the plastic) in the Reprap's firmware. This guide describes the process: http://richrap.blogspot.com/2012/01/slic3r-is-nicer-part-1-settings-and.html

Here are some prints from after the adjustments were made: