I would agree that you should become familiar with the Epson driver first. It has great capabilities and is easy to use.
You can make custom curves with QTR. I'm not sure they are any better then what using the Epson driver. If a paper you are using doesn't respond well to the available settings in the Epson, QTR might help.
Because the adjustments in QTR from warm to cool tone are linear (using a slider in the gui) it may be more intuitive then the "dart board" approach of ABW.
QTR offers the ablilty to split tone.
QTR also offers the ability to make ICC profiles for B&W. You can make these for the ABW workflow as well.
With all this said, I frequently go back to the Epson driver using ABW. I do use the QTR ICC profiles.
Peter