There are many Jewish holidays on which we not only remember, but are required to reenact and see ourselves as participating in the events we commemorate. The most obvious example is Pesach, on which "a person must see himself as if he left Egypt" (Pesachim 116b). Another good example is Yom Kippur; in mussaf we reenactment that day's Temple service, to the point of bowing down at the same occasions when people in the Temple would have.
Sukkot may be another such holiday. Sukkah is one of the few mitzvot for which the Torah gives a particular rationale: "So that your generations know that I housed the children of Israel when I took them out of the land of Egypt" (Vayikra 23:43). Part of the mitzvah's purpose is therefore to reminds us of our temporary housing as we traveled from Egypt to Canaan. We accomplish this by moving to temporary housing of our own. What is the point of this reminder?
Once you leave the desert and establish a rich and powerful country, you are in danger of ascribing your accomplishments to your personal strength, "kochi veotzem yadi", and not to God's help. Sukkot takes place at the end of the agricultural year, when fruit has ripened on the trees and the harvested grain is gathered in from the field. Specifically in this season, when you are richest and most at ease, you are most in danger of forgetting the reliance on God you learned in the desert.
For that reason, on Sukkot you are called to reenter the desert. You rely not on the walls and ceiling of your house, but on the weak and permeable sukkah. In truth the sukkah doesn't really protect you at all from the elements, and you are really relying directly on God, on His metaphorical "clouds of glory" which surround you. This is the same situation you were in in the desert, and during Sukkot you reenact it. The word "atzeret" in Shemini Atzeret is related to "maatzar", meaning confinement. Once Sukkot ends you are once again "confined" to your permanent home, no longer roaming around the desert as you symbolically did during Sukkot.
The theme of reentering the desert is especially relevant this year, at the beginning of a shemitah year. For shemitah, too, is a kind of reentry into the desert. Once every seven years, you rely not on the crops you have farmed, but on the natural growth which God has placed in the fields. It is the closest you can come to reenacting the gathering of manna in the desert. And on Sukkot at the conclusion of every shemitah year, you hold the "hakhel" ceremony, in which the entire nation gathers to hear the Torah and reenact the covenant at Sinai.
Thus, on Sukkot following the shemitah year, you return to the desert in terms of your food supply (which has grown during shemitah), your dwelling (the transient sukkah), and acceptance of the Torah (the hakhel assembly). This year we have the first two elements; we are living in sukkot and we are already forbidden to plant new crops.
Sukkot takes place at the end of one year and the beginning of the next. Perhaps for this reason we read Kohelet, which talks about the meaninglessness of the constant repetition of life. Periodically, we must soul-search and make sure we are in fact changing and advancing. To spark this process, we recreate the unique spiritual experience of the desert, with its Divine protection, sustenance, and revelation. Charged with enthusiasm from this experience, we can then rededicate ourselves to living meaningful permanent lives in the symbolic and literal land of Israel.
(Mostly from R' Yaakov Medan, some from R' Yoni Grossman and myself)