A lot of features that git had by default had to be enabled as plugins in mercurial.

The plugins were usually shipped with mercurial so you didn't have to install them separately, but you needed to know that you had to enable them in a config. And I beleive this turned a lot of people off.

I think some of the extensions were very basic stuff like graph logging and colorized output -- and mq like you said. So it was kind of unfortunate that people got a bad impression of hg from that and bounced off.

git rebase, for all its warts, was always better than mq. A failed mq-driven rewrite was destructive! (And it kind of had to be — if you were trying to edit revision 17, there was no number available for the original revision 17 because the schema didn’t allow two revisions numbered 17, so the original had be excised.)