Provisioning new Virtualbox LAMP development VMs from scratch can be dome with minimal effort using vagrant. By making this process easy and fast I can dedicate an entire VM environment for each development project I have on hand and be sure that my environment remains consistent. That last part is not new, we have been using VMs like this for years but in my experience the VMs often become too valuable because of the manual effort required for initial set up, provisioning software, and ongoing maintenance. Vagrant scripts enable me to build and destroy VMs several times a day at speed, as and when required - removing the manual overhead.
No more "it works on my machine" scenarios, keep development environments isolated and in line with production specifications.