Replacement*
Checked out
Petry, Arcobello, Hartikainen, Lander, MPS, Fedun, and Pitlick all seem to have at least possible NHL futures and they all improved a lot playing for Nelson. Marincin, Davidson, and Martindale might also if they keep developing. That's not a bad return considering the quality of the prospects he's been sent.
As for Yak coming to OKC, I don't think being in the AHL will "fix" whatever is wrong with him. Nelson demands a pretty serious two way game and doesn't allow for a lot of creativity or offensive dynamism. It'd be cool to watch him though.
Jury is out on how much the bolded improved. I would say very little if not regression. As for the others everybody but Arco has improved on an amount that is fairly expected with age and experience. The below par/on par is more the case. Again only Arco has exceeded expectations.