Far and away, the biggest headache of moving a lab is the prospect of moving every lab member - or at least finding homes for those who wish to stay behind. I want each student to land on their feet whether they come with me or not.
My post-docs look as if they are coming, which pleases me greatly. They will be invaluable in setting up the new lab. My graduate students have been much more reluctant. I am leaving a prestigious university (that is lowly ranked in my discipline) for a less prestigious university (that is much more highly ranked in my discipline). My graduate students value the name of the prestigious university and want to receive degrees from there, and I respect that. But for my first year student, I just couldn't make it work out. She will be switching advisers, and she is perfectly fine with that. I have no doubt she will excel in another group. My second year graduate student wants to move with us, but earn a degree from prestigious university. We can make it work, but OMG, what a friggin headache. I spend about 50% of my day on the phone with Deans, writing emails to admins, coordinating between the two universities - all because my student wants his degree from PU. One faculty member asked me if the student was worth all of the effort. So is he? But I have a grant he is working on, and the project would die without him. So yeah, he is worth it. We don't always see eye to eye, sometimes I'm frustrated with him, but I need him. And he needs me. We'll make it work out, but man o man, I can see why there are deans for seemingly useless offices. For crap like this, the Dean makes a call, and then it magically works.