One of the strangest effects you will see with this type of texture mapping is a distortion of the image on the surface that "appears" to move on the surface as you move around the object. This is an optical illusion caused by our expectation of what the surface should look like and the mismatch with the mapped textures. This can also be seen as straight lines that appear crooked in the texture-mapped model.
These problems occur because the Surfaces defined in the model do not match the real surface of the object. For example, model a car door with only two Surfaces describing a flat plane. The car door is actually curved and so when the image is captured from the photograph and mapped back onto a flat surface you will get distortion.
To correct this, you need to add more Surfaces. Break up large Surfaces (by deleting them) and replace them with smaller Surface that follows the surface of the object more closely. Remember that you are approximating the curved surface by a set of connected planar triangles.
The trade-off is that as more Surfaces are added, the output file will get larger and the texture export will take longer. Depending on the result desired you can do as little or as much of this as is needed to get good looking results.