I love my staggered setup & have no issues or problems with it really at all, the key thing to look at is rotations or revoutions per mile. I have a rotation per mile difference front to rear of 4. I wouldn't allow much more difference than that, 5 or 6 would probably still be ok but may get close to the point of causing occational slip detection becoming more frequent. 7 or 8 may be the point that slip detection becomes too high or frequient or that point may be ~10, 12? 15?? the higher the difference the closer you'd get to the point that the slip light would just come on & stay on all the time but that would have to be a pretty big missmatch I think. I don't know the exact amount of tolerable vs non tolerable rpm difference, but I know from what I've seen that 4 is trouble free for me so far & has no negative affects to the awd in any way really.
to put this in perspective, if your tires were 1/2 worn & you replaced only the front tires with new ones, you may have about that same difference front to rear, 3-4 rpm difference is not much of an issue really