The idea is to make it easy to develop reusbale plugins for LINQPad.

For example: LINQPad could scan a folder (say "plugins") and compile all the scripts therein. These scripts could then be added to a MEF catalog and therefore made available to all LINQPad scriptlets.

For example, if LINQPad were to support an interface ISettings which included a property called DataContext, it would be easy to add new DataContext providers

interface ISettings
{
DataContext dataContext;
}

Then when LINQPad (or a script) needed to access the DataContext it would merely use the its DataContext property, with all the heavy lifting being done by the MEF framework.