I did this when going from 6.5.4.x to 8.2.x.x.
Good or bad, I migrated my configuration using the migration tool which worked fairly well. The configuration migrated over fairly painlessly - note that the individual ap configuration capability was apparently deleted from the GUI. You can still do this from the CLI, but it's not as friendly. The AP's will take a little while to boot the first time - I remember something abouta double boot.
I would second the idea of migrating one or two over first - you can modify a specific AP's DHCP configuraiton to point to the new controller IP address. I'm uncertain of your implementation size, but I migrated ~ 1,200 ap's without much pain using this plan.