I use about 30% overlap in my pictures for which I use the lines in my display of my D70. I use "Panorama factory" to stich them with very satisfying resutls. The key to making pictures that stich well together is finding your lens' nodal point and using that point to rotate around. If you do that there should be no stitching errors aside from ghost people/cars/animals, but PF is flexible enough to fix that.

The nodal point is the point where all lightbeams cross. Here's page about the nodal point: http://www.path.unimelb.edu.au/~bernardk/tutorials/360/photo/nodal.html
Also keep in mind when using the nodal point that the nodal point shifts when you use a different focal length.

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