1. Even "Sheyarei Mitzvah" have the power to retard punishment.
2. If someone did not yet perform the Mitzvah of Arba'as ha'Minim, he must interrupt his meal to perform the Mitzvah.
3. There is a dispute about whether this law (#2) applies when one will have enough time to perform the Mitzvah after the meal.
4. An adult male should recite Hallel instead of fulfilling it by listening to a minor, a woman, or a slave recite it.
5. There is a principle that "listening is like answering."
A BIT MORE
1. "Sheyarei Mitzvah" refers to the final stage of a Mitzvah which does not even affect the performance of the Mitzvah (i.e. the Mitzvah would be fulfilled whether or not one has performed this final stage). The Gemara applies this principle to the waving of the Arba'as ha'Minim.
2. One may perform the Mitzvah of Arba'as ha'Minim the entire day (although it is preferable to do so as soon as possible in the morning).
3. Some say that he always must stop his meal on all days of Sukos in order to fulfill the Mitzvah. Others say that this applies only on the first day of Yom Tov, when the Mitzvah is mid'Oraisa. Others say that this applies on all days of Sukos when there will be no time left after the meal to perform the Mitzvah.
4. Even if he wants to fulfill the Mitzvah by listening to a minor, woman, or slave, he must repeat each word after them, but he is cursed for not knowing how to say the words himself (if this is due to negligence on his part) or for specifically ignoring the law (if he knows how to read and does this anyway).
5. This means that one may listen to another person's blessing or prayer and thereby fulfill his own Mitzvah of reciting the blessing or prayer (as is commonly done for Kidush and the blessing on bread on Shabbos).