Bought a custom II 10mm GFO a couple days ago (got delayed on the 4473 for whatever reason) I was a little hesitant cause of what I've heard of kimber before but did it anyways. What should I expect? Any must have aftermarket upgrades?

I have the same, mine was fussy with ammo when brand new. There is some different configurations of TC type ammo. Mine fed the Sig Saur 180gr RN ammo the best. I polished my feed ramp with some 600 grit emery and that helped.  All the slide surfaces need to break in, including the trigger. Now that I have about 800 rounds things are working much better. Mine is box stock, only mods I did was add the Kimber mag extensions.