I thought 'yes'. I learned 'no'. At least for cases where you have a geometric network in your feature datasets.
I haven't had any issues writing to older sql server or oracle 9.2 geodatabases, but replica check-outs to a file database don't fare as well. The check-out goes well. So does the check-in. But reconcile attempts within the 9.2 geodatabase fail with geometry errors (even if no geometry is edited).
ESRI Support used to instruct us to keep ArcGIS versions and geodatabases versions matched when editing (e.g. edit 9.2 SP5 geodatabases with ArcMap 9.2 SP5).
This is still the case in many situations despite what some may say. The only question is: for which situations is this the case? I have no idea. So if it's important data, match the application versions--just to be safe.