I had both of my babies at IRH. I think that their OB care is alright, their birthing rooms are fine, nursing care is outstanding. Their NICU is great. Post-partum rooms leave much to be desired, but pp nurses are fantastic.
Now that Kaiser has their own hospital right across the street from IRH, I'm assuming that most of the care will transfer over there though. I have heard mostly negative things about Kaiser, Southern California for care. Northern California has a much better system and coverage (I was in the healthcare industry for 6.5 years so I know). You just know how to play your cards right with Kaiser if you are going to have them for insurance.
Saddleback Woman's Hospital is great too.