So far I'm loving the improved Path Deform modifier. There are issues with object normals if you choose Flip. And the Up Vector has some usefulness, but it still lacks in a couple areas that I think should be improved upon.
First off the most serious one. If you happen to use Flip to reverse the axis, it reverses your normals. And you won't notice them unless you use a material that requires proper normals; SSS, glass, etc. This also causes issues with Alembic exporting whether you use the Normals modifier to correct it or not. Normals will flicker back and forth in Unity from any object that I have this Path Deform with Flip checked. There are workarounds, but require planning ahead for how you model your object on a specific axis, and where your starting point is on the path. I'd like the option to flip the normals back without having to throw a normals modifier on top of the Path Deform to restore them, or just prevent it from flipping the normals in the first place.
For the Up Vector:
It's nice to have a Look At option, but many times I just want it to align to the Axis Alignment of a helper, or just the world. I was animating a long object along a pretty complicated path that goes in many directions, and at some point, it is almost impossible to stop the twisting of the object without manually setting up an equally complicated Driven Rotation graph, when just having it align to the Z-Axis stops the twisting in my scenario. I basically had to fudge it by using the Look At assigned to a helper, and move that helper far, far away on the Z-Axis, to keep the edge I wanted facing up, up. The Adaptive Up Vector more often than not, just fails to keep shapes from twisting along the path unless you are working with very simple paths.
The Use Spline Normal option is pretty much useless unless you free hand draw a spline on an object. And as soon as you want to edit it or add a modifier on top of it, you may screw up those normals with no way to edit them back to your liking (that I've found). It would have so much more use if we were actually able to edit the normals of any spline, just like we can use the Edit Normals modifier to manually edit the normals of a mesh. We need that modifier for splines to make good use of the Use Spline Normals option.
Another option for alignment could be something similar to Cinema 4D spline rails, or rail path. Basically another spline running along next to the one we are path deforming to, that controls the alignment of the object following, growing, (whatever you are using Path Deform for) along the spline.
![Autodesk Design & Make Report](https://forums.autodesk.com/t5/image/serverpage/image-id/1350519iCB55845EBFC43016/image-size/large?v=v2&px=999" "Autodesk Design & Make Report")