I've always found it easier to type long strings of numbers on the number pad. I don't know why, it's not as though I ever deliberately trained myself to use it, but for me the number pad is much faster than using the top row.
Worse, if you're on a laptop a lot then this habit is kicked out the door. Enabling a numpad on the keyboard is less efficient than just using the top row.
I'm left handed; the numpad is freakin' awesome for number entry. Back when I still played games like Descent and WoW, it was also very efficient to setup the mouse for my left hand and leave my right hand on the number pad. Aim and fire with mouse, maneuver with numpad (in Descent), or action bar items on numpad (in WoW).