Indeed, the ability to work on code now and think about a commit later is freeing. As for the particular abstraction of how to represent the commit in progress... I like the working tree for that, rather than the index. It's just a better mental fit for me to unstage stuff I don't want to commit (via shelve/stash), _rerun unit tests_, do a simple diff without needing to remember the incantation for seeing what's in the index, and commit.