You can rewrite history, fix your mistakes, and generally do whatever you want. When merging, git isn't picky, either: if the code looks the same, it is the same.
In-place branching is hugely useful, just switch your tree in an instant (your editor should update the contents of your files automatically). So is the stash. Overall, it's just a useful tool that doesn't try to teach you "how things should theoretically be done", and never says "well in order to get X, you should have done this a long time ago".
The standard CLI UI is admittedly a weak-point, but it does not appear to have slowed adoption...
Bet bitkeeper regretted that decision...
Is this an example that goes against the common advice to launch an MVP fast to test the market (and then keep on improving)? It seems that the advice is valid only when there is nothing for the customer to compare the to-be-launched product to. If competing products end up launching at around the same time as yours, the advice may turn its head on you.