I haven't used Vagrant, but in the past I did write a bunch of scripts using the Virtualbox CLI and puppet to automate creation of multiple virtual machines based on the contents of a few .ini files. Vagrant appears to tackle that same problem-- whether it's more effective or not I can't say. Though Vagrant is definitely more featureful than what I'd cobbled together, I'm not sure how much more valuable it would be to me personally. But having an organized, self-documenting, repeatable way to generate a serverlike infrastructure on your development machine can be very useful (if you don't have extra actual servers lying around to play with, anyway)