Front glass was shattered after a drop. Touch still worked but was annoying.
Followed the guide and repair was easy. Some screws inside were missing from a bad repair job before so it took a little longer than expected but everything went smoothly.
Be sure to watch out for the digitizer cable getting folded up behind the screen and the lower antenna cable getting jammed behind the logicboard.
Mako Driver Kit - 64 Precision Bits
iPhone 4 (GSM/AT&T) Screen