@Cyancat I'm not sure I understand what you're trying to do here, can you explain what a "multi root template" is exactly? I don't see any reason why you would want to set a data property on a view model and then use v-with to override that value when there is many other ways you can do that.

@agonbina
Set the default data is not the issue, this issue is just about v-with, which not work properly in this case.
Here is a simple one without the default data: http://jsfiddle.net/qm2wqg8u/6/

About "multi root template":
This is a single root template: template: '<div></div>'
This is a multi root template: template: '<div></div><div></div>'
In this case, the comment block make the template as a multi root type: template: '<div></div><!-- comment -->'

Here have a complicated example which include all cases, which you could see the different caused by the structure of template.
http://jsfiddle.net/qm2wqg8u/4/

This is actually because: when the template contains more than one node, the component becomes a "block component", which means it doesn't have a root node (but rather a DocumentFragment). So directives that were attached to the placeholder like v-with are lost during the transclusion. Theoretically this can be fixed though.

+1 for a fix on this, I've recently run into this myself. As a workaround, I'm utilising inherit: true for the time being. Is this a priority to be fixed? Its a rather glaring issue imo.

Fixed!

@yyx990803
Thanks a lot! Looking forward to formal release :)