The parsha promises a bounty of brachos that will come to Klal Yisrael when they conquer and settle in Eretz Yisrael. Sefas Emes asks: schar mitzvah b'hai alma leika? You could answer by distinguishing between the yachid and the tzibur, but the S.E. answers (5648) by distinguishing between Eretz Yisrael and everywhere else. Just like Shabbos is mei'ein olam ha'ba in time, Eretz Yisrael is mei'ein olam ha'ba in space. You can't get schar mitzvah in hai alma, but Eretz Yisrael already touches another world.
"V'achalta v'savata u'beirachta..." We understand that the eating and enjoying is a benefit Hashem is promising to give us. Shouldn't the pasuk end "u'tevareich," commanding us to say a bracha? Why is it phrased as if too is part of what Hashem is giving us?
The Sefas Emes answers that u'beirachta is in fact part of the promise. When one partakes of the food of Eretz Yisrael and enjoys its bounty, one is inevitable inspired to bracha. It doesn't have to be commanded -- it is a natural outcome.
However, if you read the pesukim that follow, "Hishamer lecha pen tishkach es Hashem..." they are filled with admonitions and warnings to stay in line. Chasam Sofer explains that enjoying the fruits of Eretz Yisrael is not a positive end in itself like S.E. seems to suggest. The fruits of Eretz Yisrael have value only if they are used properly to give one strength for avodas Hashem and learning -- they are the means to an end. There has to be a "hishamer lecha" to make sure the gift is used for the right purpose because doing so is not an inevitable, natural outcome.
This machlokes echoes a machlokes betweeh the Tur and the Bach. The Tur (208) writes that when one says a bracha mei'ein shalosh, one should omit the words "v'nochal m'pirya v'nisba m'tuva," as there is no inherent value in just enjoying the fruit of Eretz Yisrael. The gemara rhetorically asks, "Did Moshe Rabeinu want to enter Eretz Yisrael just to eat its fruit?" The assumption is that to say so would be ludicrous. The Bach disagrees. He writes that the fruits of Eretz Yisrael are nourished by the Shechina itself, and by eating, we connect with G-d.
I would like to suggest another parallel. The Rosh writes that the nusach of the bracha of bareich aleinu should read "v'sabeinu m'tuvecha..." We are asking for Hashem to bestow his goodness upon us for rain, good crops, parnasa. The GR"A, however, writes that the correct nusach is "v'sabeinu m'tuvah," that we should enjoy the fruit of Eretz Yisrael. (I checked two popular siddurim and found that the Artscroll follows the nusach of the Rosh; the Koran R' Sacks siddur follows the GR"A. Neither note the other variant nusach.) Why are we sticking in a request to enjoy the bounty of Eretz Yisrael in the middle of a bracha for our parnasa? The answer comes from our parsha as well. "Eretz asher Hashem Elokecha doreish osa" -- Chazal ask: isn't Hashem doresh every land, all over the world? They answer that of course Hashem does, but it is through Eretz Yisrael that that derisha occurs. The affairs of the entire world are seen kavyachol by Hashem through the lens of Eretz Yisrael. Therefore, by asking "v'sabeinu m'tuva," wherever we are, we will partake of bracha as well.
Perhaps the Rosh's point is that if we can ask to connect to Hashem and receive m'tuvecha, why not ask for the end goal and not m'tuvah, which is the means. And perhaps the GR"A in turn holds like the Bach, like the Sefas Emes, that enjoying the fruits of Eretz Yisrael is an end, is a way to connect with the Shechina directly.