This is an interesting article (well, in large part collection of quotes/resources) on the interaction of deterministic synchronization and floating-point: http://gafferongames.com/networking-for-game-programmers/flo...

There seem to be conflicting opinions from game developers about whether you can coax determinism out of IEEE 754 floating point, if you're careful about it. From what I've read, the IEEE 754-2008 revision is supposed to take the goal of reproducible results more seriously as well, but I'm not sure how widely implemented or reliable its efforts in that department are.