What are the connotations of "Ve'ahavta es Hashem ... "?
Rashi #1: It means that one should serve Hashem out of love and not just out of fear. 1
Rashi #2 (in Sanhedrin, 74a): It means that one should ot exchange Him for an Avodah Zarah.
Ramban (citing the Sifri): One should study Torah (not in order to be called 'Rebbi', to sit in a (prestigious) Yeshivah, to live a long life or to merit Olam ha'Ba, but) out of the love of Hashem.
Seforno: It means that one should be happy to do whatever is good in the Eyes of Hakadosh-Baruch-Hu.
If one should study Torah purely out of the love of Hashem, why did the Torah write earlier, in Devarim 4:40 "Lema'an Yitav lach ... " and "u'Lema'an Tichyu u'Vasem vi'Yerishtem es ha'Aretz"?
Ramban: It is in the form of a warning - that if we don't keep the Mitzvos, we will forfeit our rights to live, or to continue to live, in Eretz Yisrael (and not as a reason for keeping the Mitzvos).
Since the Torah will say (See Pasuk 13) "Es Hashem Elokecha Tiyra", why does it need to add "Ve'ahavta ... "?
Rashi: Because someone who serves his master out of fear will desert him if he pressurizes him excessively, which he will not do if he serves him out of love. 1
Ramban (citing the Yerushalmi in B'rachos, 9:5): 'Serve both out of love and out of fear - Out of love, because someone who loves will not hate; out of fear, so that, in the event that you come to lash out, you will not lash out!' 2
What are the implications of "be'Chol Levavcha"?
Rashi #1 and Targum Yonasan: It implies that should serve Hashem with the Yeitzer ha'Ra as well as with the Yeitzer ha'Tov. 1
Ramban #1: It implies that one should control the desires of one's heart with love. 4
Ramban #2: Refer to 6:5:1:3.
Which we learn from the second 'Veis' in "Levavcha". See Sifsei Chachamim. In other words, to harness one's bad Midos - such as Ta'avah (desire) in the service of Hashem (See also commentary of Mosad ha'Rav Kook). See also Ba'al ha'Turim.
It also implies that one should serve Hashem without doubts - See Peninim mi'Shulchan ha'G'ra, Bersishis, 4:5-7.
Which we learn from the word "be'Chol". See also commentary of Mosad ha'Rav Kook.
What are the implications of "be'Chol Naf'sh'cha"?
Rashi, Ramban #2 (citing B'rachos, 54a), Rashbam and Targum Yonasan: It implies that one should love Hashem even if He takes one's soul. 1
Ramban #1: It implies that one should also love Hashem with one's mind. 2
In other words, one should be prepared to give up one's life for the love of Hashem. Ramban: According to this explanation, either the word "be'Chol Nafsh'cha" is superfluous or it means even going so far as to give up one's life with love, as opposed to merely suffering or giving up a single limb.
Ramban: As in Shmuel 1, 25:29. And it means to have the correct Hashkafos - in matters concerning Emunah and Bitachon.
And what are the implications of "be'Chol Me'odecha"?
Rashi #3 (in Sanhedrin, 74a): It implies that one's love of Hashem should override one's love for anything else.
Ramban #1: It implies that one's love for Hashem should be intense. 5
Ramban: The Torah tends to refer to one's money as 'an abundance' - See Ramban.
Rashi: Because there some people who love their money more their bodies. (See Sifsei Chachamim). (It refers exclusively to not transgressing a Lo Sa'aseh - but not to fulfilling an Asei).
Rashi: be'Chol Midah u'Midah she'Hu Moded lo, hevei Modeh Lo Me'od Me'od' - (a play on the word "Me'odecha").
Ramban: As if it had written "Me'od Me'od".