I actually obtained an offer from Yammer (Microsoft) at the same time.

This offer is what I used to negotiate Apple’s offer.

They went up a several thousand dollars in the signing bonus, but that doesn’t help much if the base salary is average compared to other medium-sized companies in the cities. A bank is not going to give a good mortgage based on compound (imaginary) income, unless I have at least one year of work experience in that company (to use tax forms as proof of income).