1) The US-Israel relationship has strengthened. It's not every day MK Danny Ayalon of the Yisrael Beiteinu party says "We have not had a better friend than President Obama" next to the chairwoman of the Democratic National Committee. That President Obama went to bat for Israel yesterday at the UN General Assembly has not gone unappreciated by the Israeli administration, resulting in strong statements of support from both sides. For President Obama, support for Israel also takes the wind out of the sails of Republican presidential candidates who accuse him of being less than supportive.
2) US soft power among the Palestinian people has degraded. The President's UN speech sparked protests in Ramallah and Gaza City. Some Palestinians feel that despite the President's rhetoric on settlements and the 1967 borders, he has ultimately thrown the Palestinians under the bus in the diplomatic sense. Given the delicate balance the US needs to strike on this issue, alienation of Palestinians may be an unfortunate but necessary cost. However, if the bid were to result in mass peaceful protests, the US would be in an even more awkward position, trying to balance its support for free speech with its opposition to the bid. Its leverage in this situation would be somewhat constrained.
3) Israel has ramped up its peace rhetoric. Given that it already has US support and that the Palestinian leadership controls the tempo of diplomacy, the Israeli administration can call for negotiations and talks without having to actually put anything on the table. By offering negotiations too late for the Palestinians to accept without losing face, Israel can point to a Palestinian refusal to engage as proof that it wants peace more than the Palestinians. If the international community wishes to pressure Israel in the future, this action will constrain its ability to engage the Israeli administration on its own terms.