I like it (specifically because of its simplicity). It's not going to work for projects that require a more complex build process using a build tool but for simple modules it's a rather elegant solution. Projects that need a build tool don't need to use it and can just continue using a build tool and manually managing their external packages (hopefully eventually using whatever gem/CPAN-style package proposal is finally adopted).
I think it's a great stopgap until the D community has the manpower to create (and more importantly, maintain) something like gem. There are certainly some details to work out but I like the overall idea.
For people new to any language the most confusing (and usually poorly documented) part is the build environment. "Where do I get this package, where do I have to put it to use it, how do I even build it?" Having to learn that for every external package you want to use is a big roadblock to anyone who is new. This proposal doesn't eliminate entirely but it does get rid of the simpler cases for those who choose to use it.
Regards,