We installed Biztalk 2004 SP1 at work here today, and in the process I discovered an exciting new approach to versioning interfaces from the Biztalk team. Rather than going to the trouble of creating a brand-new interface, and the hassle of thinking up a new name (as suggested here), they decided to just go and ADD METHODS TO THE INTERFACE. They added the GetEventStream() method to the IPipelineContext interface (which lives in the Microsoft.BizTalk.Component.Interop namespace). Wow. Why haven't others thought of this simple and clean way of versioning interfaces?
(c'mon people - what do you think? was that too sarcastic?)