D700 to X-Pro1 Advice

Hi folks - I know the D700 and X-Pro1 are different beasts. I'm currently a D700 owner and have been very intrigued by the Fuji for casual travel, family and event shots. I always believe there is nothing better than personal experience when judging cameras (as opposed to 10 minutes in a shop). So, the question is, has anyone either moved from a D700/ high end DSLR to the Fuji or found they use the Fuji more than their DSLR? I hear concerns about shutter lag, slow times between shots and auto focus being slow, especially in low light. In the real world, is this much of an issue eg for moving kids etc?