This was written for Preview 1, and MEF has done a great progress since then. Per your assertions :

>> The composite pattern is clunky, so you have to write setup code for composing the parts in batches which I find silly. Surely you can inject a configuration. Most IoC’s do this. Why do we need compiled code.

I personally favor compiled code, even though I attempted this in the past : http://www.sidarok.com/web/blog/content/2008/07/14/building-a-configuration-binder-for-mef-with-poco-support.html . You can provide your config - based parts with external configuration using Export Providers in the latest drop of MEF. (I guess there is already one in MEF contrib but not quite sure)

>> Why is there no proxy for imports? How do I intercept?

Because MEF gives you the composition hook, and you provide your logic to customize container behavior. IMHO this is done best again with Export Providers : http://codebetter.com/blogs/glenn.block/archive/2008/12/25/using-exportprovider-to-customize-container-behavior-part-i.aspx

>> Why do I have to attribute contructors, surely you could reflect parameters, and based on their types you could resolve the params, just like Castle Windsor does.

http://codebetter.com/blogs/glenn.block/archive/2009/04/27/poco-mef-and-custom-type-systems-are-you-ready-to-take-the-red-pill.aspx Be sure to read the comments especially..

>> What about ordering within the imports? Everything uses collections, you can setup cardinality but nothing so far suggests priority.

There is a MetaData that comes along with them, and you can amend this per your needs.

>> I know the MEF != IoC/DI, but there is alot they could have borrowed, instead of building this clunky, invasive attributed monster!

You can do IoC with MEF, or use existing IoC to host your extensions ( http://blogs.msdn.com/nblumhardt/archive/2009/03/16/hosting-mef-extensions-in-an-ioc-container.aspx ) but MEF indeed takes care of a lot more different things as well ( http://www.sidarok.com/web/blog/content/2008/09/26/what-is-this-managed-extensibility-framework-thing-all-about.html )

Hope this all make sense. Sorry if caused any confusion.

- The composite pattern is clunky, so you have to write setup code for composing the parts in batches which I find silly. Surely you can inject a configuration. Most IoC’s do this. Why do we need compiled code.

- Why is there no proxy for imports? How do I intercept?

- What about ordering within the imports? Everything uses collections, you can setup cardinality but nothing so far suggests priority.

- Why do I have to attribute contructors, surely you could reflect parameters, and based on their types you could resolve the params, just like Castle Windsor does.

I know the MEF != IoC/DI, but there is alot they could have borrowed, instead of building this clunky, invasive attributed monster!

I would love you hear your comments on this.