I'm a git user "forced" to learn Mercurial. While I agree that Mercurial has many of the same features as git, I feel git works much better for my workflow. The index, "git add/remove -p" and "git rebase -i" are my very close friends.
The first thing I noticed is Mercurial's rigid adherence to "committed is unchangeable". For me a commit is more a checkpoint, but it's not necessarily something finished. Usually I develop something as a series of patches, commit various bug fixes and use rebase to fold the bugfixes into the appropriate patch.
I was relieved to find the MQ extension which gives you much the functionality but with a very obtuse UI. The phases you point to seem to be a further step in the right direction. Though I feel their painting themselves into a corner since now a review tool like Gerrit becomes impossible: you push to the review tool which would make your patch immutable, while the whole point of the review is to be able to fix the patch!
Other rough edges: that the "pager" extension is not standard, there is no justification for "hg log" on the terminal filling your scrollback buffer with the entire history of your project. The "color" extension could also be better advertised.
My feeling is that git is a tool for people who deal with large numbers of branches and patches daily, and Mercurial is for people push a few patches around occasionally.