Regarding the RAW files, all the work goes into custom edits, crops, tagging and sorting. All that gets lost. Of course, you still have the original, but you'll lose most of your work.
Regarding backups, you should back up whole projects or use Aperture vaults. They contain the edits and the original files. It's a much better backup strategy. In principle if you choose to migrate to another piece of software, you can export the RAW files to whatever file format you prefer in order to keep a lot of your work.