I have a couple of suggestions on how Orcas could improve the user experience with extension methods.

1. Allow extension methods to be colored differently (i.e. in Tools | Options | Fonts and Colors)

2. In IntelliSense, have some mechanism for temporarily hiding all extension methods (e.g. pressing and releasing the shift key on its own could toggle the visibility of extension methods while the popup is active)

The main scenario for 2 is with collection types, when you want to call a method on the collection type itself (e.g. Add/Remove/Insert/Clear, etc). It's hard to 'browse' through the available methods when they're diluted with 40+ query operators.