New Housing tax credit?

Exactly how does the current first-time buyer credit (exp. Nov 30) phase out and the new one (just signed into law) begin? The old one was based on closing date, the new one is based on the contract date, so what happens if you close on a house purchase on Dec 2 on a PSA/ contract signed on Nov 15. Does that qualify for the new credit? Note that I have a client that doesn't qualify for the credit based on the current $75K income limit, but will qualify for the new increased income limit (so he needs the new credit, even though the new credit may have to be repaid if the 3-year rule is violated later). Also was there any change in the new credit terms that effects the sharing of the credit for non-married joint-owners? I believe the old one could be shared pretty much as desired with the income test applying to each person individually (so if one person was over the income limit the other could claim the full credit).