Your comments highly suggest that you are not by any means a knowledgable mercurial user. You don't have to "assemble" mercurial from parts to do history rewriting. Enabling the relevant extensions amounts to adding a single line to a config file. I usually copy the same config file around when installing mercurial anew so that I can cut out even that step.
Shelf isn't that necessary because of mq, which is bundled by default. It is very feasible to use mq as a simple shelf substitute, much easier than using it for its more complex usage scenarios. Also, for your use case, it's pretty easy to hg diff your change to a file, switch branches, and then use the GNU patch command to apply your changes on top again, so you don't even need shelf or mq to do that if you haven't checked anything in.
Ugh. Thinking about going back to that workflow makes me physically ill.
Git (as Linus says) is a STUPID content tracker. 99.9% of the time when I'm working on source code, git allowing me to do stable, local "bookmarks", keep multiple local branches (and local history) active simultaneously, and keep all my content tracked... Git has its flaws and warts but don't seriously suggest that "svn diff > ~/working-on-foo.patch" is a valid workflow. That's bringing a knife to a gunfight.
I suggest that if you can understand a linked list, you can understand git. And if you're a programmer that can't understand a linked list... well... print out your "cheat sheet", here's a copy of Tortoise, and commit your code to a branch before it gets approved for main-line.
I only suggested the diff/patch workflow for the simple case where you realized after making edits that you were in the wrong branch. It might even be possible to just update to the correct branch and have mercurial automatically try to remerge your changes, though I haven't tried to know for certain. I think you're taking my suggestion way out of context, though I could be misunderstanding you.
Mercurial has remote-trackable bookmarks now (something I felt they needed for a long time). I agree Mercurial's branch tracking in general isn't nearly as good as git's, local branches being the biggest example. There is a local branch extension for mercurial (http://mercurial.selenic.com/wiki/LocalbranchExtension), but having used it a long time ago I'm not sure I'm the biggest fan.
However, I firmly believe that mercurial is in the same league as git and both are more than good enough to get the job done, and each have their relative strengths and weaknesses. I also believe that the outspoken part of the git community tends to be overzealous and blind to git's faults and Mercurial's strengths.
Well, if I need to turn on a few extensions and download obscure python scripts just to get the minimum viable experience, I consider the "Lego" badge mine.
"it's pretty easy to hg diff your change to a file, switch branches, and then use the GNU patch command to apply your changes on top again"
It feels like mercurial developers wanted to inflict pain on me, and makes me want to hurt them in return.
See, it's three steps. It's four actually, because you also want to delete the diff file.
You know how many steps did it take in SVN? Zero.
When you switched branch, it just preserved all your changes and applied those back. You didn't have to do anything.
Maybe it didn't work when there was a conflict - once per 100 switches. But mercurial won't let you do that - that's 100 per 100 switches.
Shelf isn't that necessary because of mq, which is bundled by default. It is very feasible to use mq as a simple shelf substitute, much easier than using it for its more complex usage scenarios. Also, for your use case, it's pretty easy to hg diff your change to a file, switch branches, and then use the GNU patch command to apply your changes on top again, so you don't even need shelf or mq to do that if you haven't checked anything in.