I have been working with MEF for about 2 weeks. I started thinking about what MEF is for, researching to find out how to use MEF, and finally implementing a Host with 3 modules. The contracts are proving to be easy to grasp and the modules are easily managed.

Although MEF has a very practical use, I am wondering to what extent? I mean, is everyone going to be rewriting existing applications for extensibility?

Yes, that sounds, and is insanely impractical. Rhetorically speaking:

• how is MEF affecting the current trends in programming?

• have you begun looking for opportunities to use MEF?

• have you begun planning a major re-write of an existing app that may benefit from extensibility?

That said, my questions are:
how do I know when I should plan a new project with extensibility?
how will I know if an existing project needs to be re-written for extensibility?

Is anyone using MEF?