need ability to specify layout per controller

You can, if you have a controller BookController just create a layout called:

grails-app/views/layouts/book.gsp

You can also do per action layouts:

grails-app/views/layouts/book/list.gsp

I'm not sure how carefully you read my post

I'm aware of the naming convention and the ability to override it per view, but for some reason you cannot do it per controller. For example, if you have a BookController, and a MovieController, and both use the same layout, why not allow them both to specify the same controller:

BookController{
static layout = "product"
}

MovieController{
static layout = "product"
}

If you have many views per controller, specifying in each view is tedious and violates DRY, and the controller is the most likely level of granularity for layout changes.

Ok we'll look to support this post 1.0

Totally agree on this one, and it should also be possible to change layout per action. For example in Rails you can do it like this:

class MyController < ApplicationController
  layout "main", only [:index]
  layout "admin", except [:index]
  ...
end

A layout may be specified by assigning a value to a static property named "layout" in a controller:

class BookController {
    static layout = 'customer'
}

Views rendered from that controller would be decorated with the grails-app/views/layouts/customer.gsp sitemesh template.