My favorite siddur these days is the Koren Sacks Siddur. Busting ArtScroll’s liturgical monopoly for the first time in a long time, Israeli siddur and Tanach publisher Koren combined the elegant layout and typefaces created by Eliyahu Koren with the clear, concise English commentary and instruction of the British Sacks siddur to create the Hebrew-English Koren Sacks Siddur. The siddur came out this summer and quickly shook up the exciting world of Orthodox American liturgy.
One of the OU’s perennial complaints about the ArtScroll family of siddurim is their refusal to quote or cite modern sources. The OU has long sought to create a siddur that includes the commentary and teachings of the giant of Modern Orthodoxy, Rabbi Joseph B. Soloveitchik. Koren loves it and is already working on creating this siddur, which they call the Mesorat HaRav Koren Siddur.