
Buildout is open source and extremely flexible. It also has a large number or third party add ons that make it easy to integrate any workflow you want. I use buildout with a modified django recipe to deploy app 'snaphots' to our servers that can be rolled back or forward if there are any app errors. I also integrate with Newrelic's API, Github and Buildbot as part of a continuous deployment system that allows any developer on the team to deploy to live or test environments in a matter of seconds. Review collected by and hosted on G2.com.
The only issue I have with Buildout is it's builtin dependency on Pypi. There have been issues where Pypi has been down (once or twice a year) and we have been unable to bootstrap apps. Fortunately such issues are usually easy to work around for me but they have occasionally interfered with development.. Review collected by and hosted on G2.com.