version vs. static if

[Adam Ruppe]

There's several reasons backward compatibility is important:

1) Breaking it annoys me. There's still stuff I like for new features,
   so I'm not at the point where I'll never update again yet, but I
   don't want my code to break more. Especially if non-trivial.

2) It splits people. Suppose you grab a lib and it uses D3 features.
   If you're on D2, you can't touch it.

3) It gives a perception of instability. There's already enough
   complaints on this about D1 and D2.

With the costs, the benefit has to be huge to break compatibility.