I am assuming you are referring to CAD import and export using neutral file
Import
import diagnostic
Import diagnostic and automatic repair work pretty well if the error is "small" enough, eg: some broken surface or small gap. However, if it involve ZTG (for example sheet metal export from CREO which allow ZTG...) import diagnostic most probably wont work and I would always end up manually repairing the file
Tip/Trick:
As we have 2 different CAD system, sometimes if I could not get a file to import properly in 1 CAD system (eg: SOLIDWORKS), I will import the file to other CAD system (CREO) and reexport it.
For example, recently i came across a really messed up CAD done by a freelancer (the step is all "broken surfaces) that i could not import to SOLIDWORKS, I ended up open it in CREO and reexport it as parasolid to be imported in SOLIDWORKS
Export
Most of the time i just stick with STEP214
Parasolid work well if it is SOLIDWORKS→SOLIDWORKS, but sometimes it got messed up pretty easily in other CAD.
Once thing with export that i still could not find a satisfactory solution for SOLIDWORKS is on how to indicate tapped hole in exported file
As the STEP export do not include cosmetic thread, it is hard to know which hole is suppose to be tapped hole, especially when the part has large number of hole of different size, and mix of tap and clearance hole.
Drawing helps, but some times 4X M3 hole callout in the drawing did not really tell where the other 3 hole is suppose to be..
Sometimes, I will end up "coloring" the hole feature to indicate which hole need to be tapped.
For creo, the tapped hole will be exported with additional surface body so i have less issue with tapped hole