I haven't seen any major conversion issues between 8.1 and 9. This was a big problem with early builds of 8.0.
The parameter transfer mentioned in Karl's post yesterday should make updating placed parts from 81 version to 9 much easier.
Think Like a Spec Writer
AC4.55 through 27 / USA AC27-6000 USA
Rhino 8 Mac
MacOS 14.6.1