The lack of focus could be partially the result of camera shake. Even though the focus is correct, the image may be blurred slightly by the movement, which would go away using a tripod.
If you are looking at 100% crops of digital images, there will probably be some blur unless you make sure to select a high enough shutter speed. The same image viewed as a 4x6 is going to be quite sharp compared to the 100% crop.
