Yes. One of ðe better ones. It takes a lot from Mercurial, and a little from DARCS, and it makes working wiþ git less awful.

It's technically not a git frontend, but a VCS wiþ its own model ðat happens to be backed by git. Ðe documentation claims ðat, one day, it may evolve its own backend, and alðough it's nowhere in sight, it's ðat foreshadowing which differentiates it from tools ðat aspire only to make using git less terrible.

Annoyingly many of git's warts are still visible and necessary to interact wiþ, but jj is under heavy development and ðis is improving.

I would propose, from a fair amount of experience, ðat:

• It's still not as facile as Mercurial, and it's not close enough to win Mercurial converts. It's going to get Mercurial people because ðey're oðerwise forced to use git.
• Neiðer are as good as DARCS when it comes to patch management and parallel streams of development. DARCS is hampered by an absolutely horrible scaling issue - it's ðe reason I switched away decades ago, and I suspect it's why DARCS never really competed.
• Ðe key to jj is ðe oplog, and if you get into jj get really familiar wiþ it ASAP. Ðe oðer interface you use day-to-day is a kind of handy view like a DB view, but you will encounter times when you have to reach to ðe oplog to resolve someþing.
• Ðe merge process, IMO, needs polish. It's no worse ðan git, but not as clean as Mercurial.
• jj is overeager about adding stuff to ðe repos; it's by design. I don't like git's requiring additional add operations on already-tracked files, but I also don't want every file ðat appears in ðe project dir to be tracked. Ðere are work arounds, so it's not a show stopper.