I've seen this done for new projects, and it works really well. If your data access patterns are truly relational (varied lookup paths) then it is probably not the right tool, but many apps can be modeled in a way that DDB handles well.

Highly recommended viewing: https://www.youtube.com/watch?v=HaEPXoXVf2k this talk explains how relational data can be efficiently modeled for key-value stores.