1) “Vayis’u m’Refidim va’yavo’u midbar Sinai…” (Shmos 19:2) Rashi asks why the Torah has to tell us that Bnei Yisrael journeyed from Refidim -- we already know from 17:1 that this was their starting point, the spot where they were camped. Furthermore, the pasuk immediately preceding this one tells us that they came to Sinai – why repeat this detail as well? Rashi answers that the Torah is connecting the arrival at Sinai with the start of the journey: just as the people did teshuvah when they left Refidim, so too they did teshuvah upon their arrival at Sinai.
If the people did teshuvah when they left, why did they need to do teshuvah again when they arrived?
We see from Rashi that when a person has an uplifting experience (e.g. an inspiring Yom Tov like Shavuos!) what passed for adequate avodah beforehand no long cuts it. What was adequate teshuvah before the arrival at Sinai no longer was good enough. The new experience of Sinai demanded that Bnei Yisrael revisit the past and improve further on what they had done beforehand. A second, more meaningful teshuvah was now needed.
2) My wife pointed out an interesting Midrash that says that Rus and Naomi travelled back to Eretz Yisrael on Yom Tov in violation of the issur techumin. This stands in contrast to the gemara that interprets “asher teilichi eileich” was a response to Naomi warning Rus specifically about the issur techumin. The Shvus Ya’akov suggests that the mitzvah of yishuv ha’aretz overrode the mitzvah derabbanan of techumin. It was because Naomi took this extraordinary step of violating the issur for the sake of returning to Eretz Yisrael that she warned Rus that this was not the halachic norm. This chiddush is meduyak in the pesukim: throughout the perek the megillah refers to “Beis Lechem Yehudah”; however, Naomi is described as returning “lashuv el Eretz Yehudah.” (1:7) Why not “Beis Lechem Yehudah?” Because Naomi did not return all the way home. Once she was in safe territory in Eretz Yisrael she stopped travelling and so as to not exceed the techum more than necessary.
From the megillah’s opening with of Naomi violating an issur derabbanan for the sake of returning to the land through the end of the megillah where Boaz concerns himself with the geulah of the fields, one of the overarching themes of the sefer seems to be this topic of yishuv ha’aretz.