Shavuos was one of the three fixed times of the year when Breslover Chassidim came to the Rebbe. Therefore, in recent years many Breslovers travel to Uman to spend Shavuos near the Rebbe’s tziyyun. (However, there is no requirement to do so; the only time a Breslover Chassid is obligated to travel to Uman is for Rosh Hashanah.)
The first day of Shavuos is one of the five times of the year that Breslover Chassidim are particular to daven together ki-vasikin, following the custom of the Baal Shem Tov.
Rabbi Nachman greatly praised the medieval poem “Akdamus Milin” and the regal melody with which it is sung. This remains a highlight of the Shavuos davening in Breslover shuls today. It is our custom that each stanza is sung by both the chazzan and the congregation, not by alternating stanzas, as in some communities.
(See Sichos ha-Ran 256)