Phabricator

Phabricator is phantastic. Host your own phabulous installation or pay for hosting as a service. Four out of five ex-Facebook engineers agree it's the best open source version of Differential available!

I recently came across this and discovered that Phabricator is pretty robust. I'm looking forward to trying it out :)

Seriously, Phabricator is great, things like diffusion make it great for developers.

But the setup should be way more quick and easy, and the phacility hosted version should really be something like £10/month flat price

Pros:

All the applicatons are really well made and work amazingly.

Cons:

It's *really* hard to set up if you have no idea what you're doing and £5/user/month for the phacility hosted version is a bit much