Check out this thread and download the sample tune and the Xcalibrator's tweaking software. It should give you a feel for what the Xcal offers.
http://www.modularfords.com/forums/showthread.php?t=20435
I just checked out the SCT Extreme Tune (also known as QuickTune) using the sample tune file posted in the thread. It allows you to adjust for gears and tire size. It allows you to adjust spark timing from -5 to +2 degrees. It allows you to set idle RPM. It allows you to set part throttle and WOT air/fuel ratios. It allows you to set the speed limiter to stock, none, 30 MPH or 70 MPH.
It does NOT allow turning off the Traction Control. It does NOT allow adjustments to the Cooling Fan On/Off temperatures for High and Low speeds. It does NOT allow you to turn off the EGR System. It does NOT allow you to turn off the rear O2 sensors, which means you'll still need to buy MIL Eliminators.
I did not see any adjustments to the auto trans shifting at all. No shift pressures. No shift points. No torque modulation. Nada.
None of the help screens work.
The Predator lets you do all that directly from the Predator unit itself, plus data logging and OBDII code reading. Not bad for a "Gameboy"...