Justin Carmony has shared his success story about the use of Vagarant and PHP as a platform to make setting up and configuring developers' environments simple.
Now-a-days, you have frameworks that need to be setup [as a part of your environment], include paths that need to be changed, modules that need to be installed, web servers that need to be configured for your routing, etc. Then you might not just have MySQL, but Redis, Mongo, Couch, Memcached, Postgres, or any other dozen other servers. Then in Production you might have load balancers, multiple web servers, clusters of databases, and the list goes on. Simply put: web development environments are complex.
He introduces Vagrant and talks a bit about how it helped them with the setup and configuration of two new remote developers they had limited contact with. After some initial quirks, Vagrant made it simple for them to get up and running with new environments in a day.