This is awesome, I can't wait. I've been waiting for this!
Most of my projects right now have had all of their Vagrant plugin dependencies, including Vagrant itself, in the Gemfile because I wanted to make sure any developer could get a workable development environment without worrying too much about Vagrant versions. On one hand I like the fact that I can install up-to-date plugins this way, but on the other hand I just want it to work out of the box.
Although I doubt we'll be able to get away from this. More likely it will cause other frustrations such as needing to override a plugin with a monkey patch, etc.
It's cool to think that the only requirement for anybody to jump into a Gradle project is to have the JDK installed. "git clone <project>", "./gradlew assemble" is all it takes for you to fetch all your dependencies and build the project.
I think it'd be interesting to see if Vagrant could incorporate something like this; it sounds like it would help your use case.
Sounds like a commercial. Many people have good things to say about Gradle's functionality, but too bad about the programming language I have to use with it, i.e. Groovy, at an old 1.x version, with a bloated grammar spec using an old 2.x version of Antlr, i.e. http://svn.codehaus.org/groovy/trunk/groovy/groovy-core/src/...
Too bad I can't use a language with a simplified easy-to-remember grammar, like Scala, to program Gradle.
The latest Gradle release notes http://www.gradle.org/docs/current/release-notes always mention both Groovy and Scala when describing how to build projects, but all the build script example code is in that Groovy language. Will Gradle ever expose an API so developers can choose to use the same language for the build scripts as they do for the projects they're building? Perhaps even ship Gradle with different build language options?