I think this is all about the trade-off between the verbosity required for standard configuration on one hand and the complexity and feasibility of exotic configurations on the other. The XML namespace for Spring Security was unfairly favoring standard configurations by being very concise in those cases. Less common configurations were much harder to get right and exotic ones were a nightmare.
The litmus test for this effort should be: Can the user achieve every possible configuration without introducing new mechanisms? One shouldn't have to write a BeanPostProcessor or a namespace handler for a particular configuration. Neither should one have to translate one configuration syntax into another, XML using namespaces into plain XML beans for example. If that means that common configuration be more verbose, so be it. I'd rather climb an initial hurdle of learning all the building blocks – if the building blocks empower me to do everything I want – than a trivial first step with a large paradigmatic gap to the second one.