I generally come from the World Of C-Likes, so it has always been explicit ones for me.

When doing development, I write as if nothing were imported, and only import things as I find I need them. Periodically go through and trim out units I no longer need. I see no reason to change; while it might be a little faster coding by importing more and leaving in unnecessary ones, I find decreases the quality of my code. My currentway makes it easier for me to do loosely coupled interfaces, highly modular implementations, and makes me think about what I'm importing (well, including) and why.