Gerrit itself is an interesting review tool. It uses Git references to manage the review changeset before it is merged into the parent branch.
I used it on a project that used Redmine for issue tracking and Gerrit for the git repo and review tool. It took a bit to get used to how to git to push changes to a Gerrit review so we ended up using Git extensions to manage that.
Not even close. I have another comment where I get into some details, but, no, three's no overlap beyond the fact that Gerrit pulled some UI and workflow things from Critique (and Mondrian before that, the tool that predated Critique)
Gerrit is awesome. I will never, ever go back to github.
They are two entirely separate codebases, built on two entirely different revision controls systems -- one open source, the other not -- with Gerrit inspired by Critique, not the other way around. Yes there are similarities be tween it and Critique. Because Googlers worked on both.
IIRC Gerrit is an open source re-implementation from scratch of Critique.
I agree Critique is much nicer, but mostly because it's more consistent and doesn't have to deal with all the oddities of git.
Gerrit does in fact impose a particular workflow: each commit is the atomic unit of review.
This, BTW, is a beautiful thing. Most of the idiocy of github is trying to have multi-commit pull requests. Then they had to bodge on that "suggested changes" nonsense instead of having proper dependency tracking between pull requests.
When each commit is the unit of review, you get pull request dependencies and recursive pull requests automatically. Instead of suggesting changes you can simply create a commit with your suggestion which has the reviewed commit as its parent. It's so simple yet so much more powerful.
Graphite[0] is also similar in that space(code review platform built on GitHub), the CLI could use some work but combined with the web UI it scratches that same itch that Critique did for me