Tim Sweeney is the founder of Epic Games and the person behind very famous Unreal game engines. John Carmack,Tim Sweeney have been some of my heroes from gaming world.
Imperative constructs are vital features
that must be exposed through explicit
This is precisely the argument Haskellers make every time someone complains about algorithms that are difficult to formulate functionally.
I am not sure I buy that lazy evaluation is too costly either, as it is actually what buys performance gains in some areas. That was a broad statement and it doesn't hold everywhere but I just want to say that it isn't cut & dry like you make it sound.
I would say the only argument he makes against Haskell that I totally agree with is its inference engine. I have very mixed feelings about type inference. It is very nice because it makes everything so concise, yet I often find myself writing function types just for clarity. Also type errors are not fun to track down as he shows in the slide.
Please note I said "nervous", not "I would never consider it ever". Another couple of years of development and I might be less nervous; Haskell has been making a lot of progress lately. Some stuff in the absolute inner core might still be C or Assembler, but I could see the bulk switching to some other language.
These days it's hard to even buy a computer with less than a gig of RAM, but the Playstation 3 - the most powerful console of the new generation - has only 256 megs. Granted, they're 256 really fast megs, but it's still a tiny amount of space by modern standards. You don't even have a hard drive to swap to when you run out of space - if a memory allocation fails, you work around it by hand or you crash.
If you're going to write a game engine that's meant to run on consoles, you really need fine-grained control of all the memory allocation in your system. That'd be my big worry with Haskell, more than speed or garbage collection latency or whatever.