I'm quite new (about one hour) here as well. I hope I may post a reply anyway?
I have this far stayed at 6 (I think) different IHG properties. Everything has been flawless, customer service excellent and Ambassador upgrades just great. BUT I have also had to contact PC and Ambassador customer services several times and they are a joke. I guess they copy&paste their answers from some manual or something.
Ie, my opinion: IHG hotels are good, membership customer service terrible.