@Stilgar: We won't do something that feels like a breaking change. If that's the best we can do, we won't do it. I'm not hell bent on the nullability feature. I'm determined on chasing it all the way to the best we can possibly do. If that's not good enough, then we'll put the feature to rest knowing that it just doesn't have a place in C#.
@PurityControl: It's a great idea to allow functions with out parameters to be called as if they were tuple-returning, having the compiler do the magic like in F#. Another possible convenience is allowing a tuple to be passed to a function that can take the individual members of the tuple as arguments.
@N2Cheval: Sounds like a big feature. We'd probably need to see a somewhat more fleshed out proposal to understand what you are getting at. But I have to say that reifying more metadata at runtime is not the direction I see us going. On the contrary, with native compilation we are challenged by the ubiquitous access to even the metadata that is there today. But maybe I'm misunderstanding the proposal.
@Alex: I don't think it's borrowing from Swift as much as borrowing from the same places that Swift is borrowing from. :) However, I see Swift doing something we've also often done, which is to take concepts from less widely adopted languages and pulling them into the mainstream. Option types (or "optional types" as the Swift guys call them, which irks me because that used to mean something else) are a well known pattern from functional languages that Swift has - rather successfully I think - integrated into a more imperative setting, and found a way to blend with the legacy Objective-C libraries. That integration depends heavily on pattern matching to do the null checking (like in the functional languages it comes from). I don't think we have that option (no pun intended), because we already have established ways of checking for null in C#. Any feature we do here would have to recognize when folks are checking for null, rather than force them to do it in a new way. That would be a disaster!