(Similarly, the Shabbos before Rosh Chodesh is when we usually recite birchas hachodesh as the potential for the upcoming month comes into the world on that Shabbos. The exception is te Shabbos before chodesh Tisrei where we do not bentch rosh chodesh because bri'as ha'olam was not preceded by a Shabbos.)
2. The meforshim struggle to make sense of the rasha's response to the tochacha: "Shalom yi'hiye li ki b'sherirus libi eiliech..." M'mah nafshach -- if the tochacha means something to the rasha, then why will he think he will have shalom? And if the tochacha had no effect, then what good will the threats in the rest of the parsha do?
The sefer l'Horos Noson explains the pasuk in light of Chazal's teaching that "Gadol hashalom," as Hashem promises to go easy even on idolators so long as there is peace among them. The rasha who hears the tochacha is scared, but he thinks he has an out: "Shalom yi'hiye li," I'll play nice with others and foster shalom and achdus, but I'll do it for the purpose of, "Ki b'sherirus libi eiliech," because I want to continue to be a rasha and not be punished.
Hashem is willing to ignore everything else when shalom is truly valued; however, if making peace is just being used as a "matir" to try to get Hashem to overlook other problems, then no dice.
3. The Torah in VaYeilech descibes how the idolator will finally come to recognize, "Al ki ain Elokai b'kirbi metza'uni kol ha'ra'os ha'eileh." Sounds like we are dealing with someone who is engaged in teshuvah or at least on the road to teshuvah, someone who realizes that Hashem does not approve of what he is doing. Yet, Hashem's response (31:17) seems far from welcoming: "V'anochi haster astir panei... al kol ha'ra'ah asher asah." Why is this ba'al teshuvah or potential ba'al teshuvah met with even more punishment, with Hashem hiding? Why slam the door in his face?
Ramban answers that the teshuvah here is incomplete -- it's a teshuvah b'lev, an introspective realization, but not a teshuvah that is accompanied by any verbal commitment, viduy, or action. That teshuvah is enough to stop the harsh punishments of the tochacha, but not enough to cause Hashem to come out of hiding (kavyachol) and reveal the light of geulah.
Yet the question is still troubling. The gemara (Kid 49) says that if a rasha is mekadesh a woman on the condition that he is a tzadik, the kiddushin is chal (m'safeik) because perhaps a thought of teshvah passed through the rasha's mind and that is enough to change his staus to tzadik. Why not apply the same standard here?
R' Tzadok says a pshat that you have to be R' Tzadok to say, and it all hinges on the one little word "al" in the pasuk. R' Tzadok says the pasuk does not mean that Hashem will hids his face because of the evil done by this rasha. Aderaba -- the pasuk means that Hashem will hide his face from the evil done by the rasha and refuse to look at it! Despite the rasha having only a hirhur teshuvah b'lev, Hashem is willing to overlook and hide himself from seeing the misdeeds.
I would answer for the Ramban that perhaps once a person has come to the point that they recognize that they had been on the wrong path, they already have a hirhur teshuvah, continuing to remain in that state of hirhur teshuvah without translating it into some concrete action or change is indeed a further indictment. The gemara in Kiddushin is speaking only about the immediate effect this first step of hirhur has on the individual's status. The Ramban is speaking about what happens when this first step is never more than a first step.
4. One final halachic point. The Rambam has an interesting din describing hakhel (Hil Chagiga 3):
אפילו חכמים גדולים שיודעים כל התורה כולה, חייבין לשמוע בכוונה גדולה יתרה.
Super-kavanah (kavanah gedolah y'seira)! Do you find such a din anywhere else? And where did the Rambam get this from?