The Kab Ha’yashar (Rabbi Shemuel Aharon Shemuel Kaidanover, 1614-1676) writes (listen to audio recording for precise citation) that although no explicit mention of G-d’s Name appears in Megilat Ester, there are a number of allusions to His Name through Rasheh Tebot and Sofeh Tebot (combinations of first and last letters of successive words). He says that one who is familiar with these allusions should have them in mind during the Megila reading on Purim. The Kab Ha’yashar emphasizes that there are special powers and secrets that become accessible at the time of each holiday, and there are "new, holy worlds" that we can access with the right concentration. All this sanctity, he says, begins at the time of the reading of the Megila. As such, both the reader and the congregation should be filled with awe and reverence at the time the Berachot are recited when the reading begins, and should have in mind that the reading of the Megila – which is associated with the word "Le’galot" – "reveal" – should reveal the special spiritual lights associated with the reading.
The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in his work Torah Li’shmah (195; listen to audio recording for precise citation), writes that it is proper not to leave the synagogue during the Megila reading, even if one had already heard or read the Megila earlier. Just as one should not leave the synagogue during the reading of the Sefer Torah, it is proper not to leave during the Megila reading, even if one has already fulfilled the Misva.