I'd like to use the csv to import nodes with their authors by username. Currently, you can achieve this by using Mapping for Node processor to add a source field for uid to the csv. It'd be nice if you could also do this by username. The only other way to do this by username is in the node processor settings, and it only allows one username per batch, either specific author or anonymous. Anyway, it's just a nice to have as the essential functionality is already there.