The Vita-Saw's smoothing groups are nonexistant. Every part of the model is smooth shaded, causing ugly lighting all over. Additionally, the Vita-Saw has no LOD (level of detail) models. When a model gets far away from the camera, or the game's model quality settings are set to medium or low, the model switches to a version of itself with less polygons. Since the Vita-Saw has no LOD models, it uses its high-poly version no matter what. Lastly, the Vita-Saw's texture has incorrect LOD settings applied to it, which cause it to use a lower-quality texture by default.

This submission fixes these 3 issues:
-The Vita-Saw now has smoothing groups.
-Added LOD models for the Vita-Saw
-The Vita-Saw's textures no longer have incorrect LOD settings

Interestingly, the update history for the Vita-Saw claims the issue with the smoothing groups was already fixed:

Originally posted by TF2:

December 2, 2010 Patch

The mesh's smoothing groups were fixed resulting in a clean, hard-edged look as opposed to the molten appearance it had before.

Perhaps it was fixed at one point, but it certainly isn't as of posting this.