I went ahead and set the posts per page to 50 globally. At this time there isn't a way for users to change this setting.
I looked on the xenforo support forum and you are correct, the setting has to be made globally. There is an add-on to add this capability but if you have the global setting at 50 that is sufficient for me and I suspect most everyone else.
Great job on the upgrade. I haven't seen anything I don't like and many things I do like. One new "feature" in particular I though was amusing was that when I viewed my ignore list, which is pretty extensive, the status of the user was displayed. It was with more than a little satisfaction I saw that probably 50% of the people I'd ignored had been subsequently banned. Keep up the good work there!