Kitchen ceiling uneven after removing soffit
To be perfectly honest with you it may actually be easier and less overall work to remove the rest of the kitchen ceiling and redo the whole thing with new drywall. 

This would be especially true in the case where the kitchen ceiling is enclosed by walls or other partitions. If the ceiling merges into the ceiling in another room then the suggested process may be a bit more work. I still think though that a merge patch in the ceiling between two rooms may be less work to make look right than the type of patch work required to fixup just where the cabinet soffits were located.