As you can see, the extensibility model of Unity works in that we can add
interception to Unity. So, we can start thinking about moving our cross
cutting concerns to these layers should we so choose if Unity is your container
of choice. There are plenty of containers out there to choose from, so
it's best to give them all a try and pick one based upon features, programming
style, and heck, maybe even licensing.
UPDATE: It looks like the Interception Extensions that Matt mentions in his post only work with Unity 1.0. Hopefully someone will update them for Unity 1.1 soon.