We're doing a lot of adjusting around here, too ... ODD is 29 months.
As far as how Isabel has reacted to Olivia, I think she's done incredibly well. I haven't seen any jealousy or anger directed at Olivia, and Isabel has been incredibly empathetic when Olivia cries. She wants to be involved with her and doesn't seem at all put off by DH or I holding Olivia or snuggling with Olivia, or even the fact that mommy's been sleeping on the recliner with Olivia since we got out of the hospital, because laying flat in the bed post C/S is just a bit much.
But we are also dealing with the more subtle effects - behavioral regression, some out-of-control type stuff, more tantrums, less responsiveness to requests to clean up or to stop doing something. I had so desperately hoped that delivery would equal a complete end to the lack of patience I had with Isabel while I was pregnant, but sadly, it did not.
I've found that involving her and giving her as much power and control as I can seems to alleviate the worst of the behavior. By that I mean stuff like: "Isabel, can you help mommy for a minute and bring me the Boppy you used with orange kitty?" "Isabel, when this show is over, you will need to turn off the TV" "Do you want to walk out of the pantry on your own, or should I ask daddy to carry you out?" That way she can be involved, or she's gotten a head's up on what's coming or, in the case of the pantry (she's where she shouldn't be), she can control how she leaves - and generally if she has the decision-making power and the opportunity to do something herself (i.e. turning off the TV, bringing me the Boppy, walking out of the pantry) it really seems to defuse the worst of her temper and tendency to fall to the ground sobbing "No!"