>before you know it some people will demand features that are not supported by it Eh, what? Features don't matter. It's just the data that should be portable.

>before you know it some people will demand features that are not supported by it Eh, what? Features don't matter. It's just the data that should be portable. If one platform supports "dynamic playlists" (which is just the equivalent of a view in SQL) and another platform doesn't, that might be a bit inconvenient, but it really doesn't matter. At least your data can be converted.