You mean other than the fact that he beat every Southern general sent against him? If Grant was that bad then what does it say about his opponents?
Grant was absolutely a great general. He was a master of maneuver warfare as he showed in the Vicksburg campaign, and bested Lee when attrition was called for. Lee himself complimented Grant, so criticisms of Grant's generalship are always lame.
But YOU know that. :)
The American way of war owes a LOT to the way Grant did things.
Walt