One of the questions that came up on our Cider newsgroup was whether Sparkle and Cider would support the same set of extensions and extensibility points. 

To answer that question, it's good to clarify that in the Cider and Visual Studio world, there are two kinds of extensibility: Visual Studio extensibility (think VS addins) and the Cider Designer extensibility (think custom property editors, design time actions, custom adorners and licensing etc.).  This post is referring specifically to the Cider Designer extensibility.

Our high level goal is to share a single extensibility model with Sparkle -- we don't want to make our customers develop more than one design time experience for their controls or have a negative experience when transferring controls from one designer to the other. 

Having said that, there are a number of challenges in accomplishing that single extensibility model for our v1s, namely the differing release schedules, priorities and target customers.  Nonetheless, we believe that we will be able to put together the right user experience by supporting different subsets of the same extensibility model with reasonable fallbacks in both Cider and Sparkle.

Which extension points do you most commonly use and what are your scenarios for writing a design time experience for your controls?