I don't know Dan's work/thinking well enough to anticipate what he might talk about. But if someone wanted me to speak on this prompt, I would talk about modern examples where optimizing compilers significantly underperform hand-written assembly:

- LuaJIT's interpreter (here is Mike Pall's famous post giving a detailed explanation of why this is, incidentally prompted by a question I asked: http://lua-users.org/lists/lua-l/2011-02/msg00742.html)

- x264, which has extensive acceleration implemented in assembly for a/v codecs (they even built their own assembly abstraction layer: http://x264dev.multimedia.cx/archives/191)

- GMP, which has extensive acceleration implemented in assembly for arbitrary-precision arithmetic.

I wouldn't go so far as to argue that any of this implies the death of optimizing compilers, so I will be very interested to see what Dan has to say.