using each others files in v8 and v8i will have very little in the way of levels and text etc as they are really the same format.... only 3 areas I know will be problematic
1. export to V7 can cause shifting ..due to limited design plane size in v7
2. graduated fills are only in v8i
3. only v8i has geographic coordiante datum setting tool for reprojection on the fly or on ref attachements of different projections being reprojected will fail in v8 and land in the wrong place yet look perfect in v8i...
solution merge the ref into the active v8i file so it reprojects to active datum and becomes the active datum file so v8 will see it in the right place..this will also happen to rasters that are not in the same datum or projection as the active file.. v8i will reproject to active datum .. where as v8 will not...
solution make the upgrade for everyone and get over it.. you / we did it for v7 to J to SE to V8 to XM and XM to V8i
and windows 3.1 to xp and now win 7 so why not v8i .. one install one platform for everyone.. IT will love you for this...