Getting new developers up to speed quickly on a project is critical, and thanks to the magic of virtual machines this is now much easier for us to do. We have a base machine image for each project, which is configured with the exact OS and software packages as the production environment. Now, 99% of the time, if it works on a dev box, it works on the production box.
But, managing all these different VMs is now getting to be somewhat of an issue, so we have started using Vagrant, which is really good at making VM use as seamless as possible. The whole point of what we do is to write code, and all the time spent on configuration to get there is wasted.
Vagrant and VMs help us spend less time shaving yaks.