Launchpad is a platform for open source projects that uses the Bazaar VCS and also supports Git too. Both Launchpad and Bazaar are developed and maintained by Canonical, the company behind Ubuntu. A lot of well-known and widely used software are hosted on Launchpad.
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Pro Great bug tracking features
Launchpad is built to be used for open source projects, as such it needs a powerful bug trackers to allow developers who want to contribute to jump right in. Launchpad displays bug statistics (total number of bugs, number of bugs fixed etc...) as well. Bugs can be searched and displayed from every project hosted on Launchpad or for single projects.
Pro Support for web based translation
Launchpad makes it easy to translate free open source projects into virtually any language in the world. Users are allowed to start working on translating any project they want just by having a Launchpad account and a web browser. Most of the time they don't have to even join a team to start working and the editor is web based, so there is no need for any special software.
Pro Integrated build/deployment system
If you use launchpad, it gives you a build system (on their platform) as well as easier deployment - user merely adds your PPA to their sources.list file. Deployment (on Ubuntu, at least - other debians as well) doesn't get simpler than this.
Con The web interface is complicated and hard to use
Other project hosts such as GitHub, BitBucket or GitLab have easy, simplistic UIs that help new and experienced developers alike to browse code right through the browser. LaunchPad on the other hand is very weak at this. Most of the projects have poor (if any) documentation and no way to determine a project's worth easily. The fastest way to do so with LaunchPad would be to download the project and look through the code manually, which is quite tiresome.