Malbim: V'Hinei is always a Chidush. Bo'az did not normally come to the field. This was a Mikreh via Hashgachah. "Ba mi'Beis Lechem" hints to a new matter enacted there (refer to 2:4:2:1).

Malbim, from Brachos 54a: Bo'az and his Beis Din enacted to greet people with Hashem's name, with the Sanhedrin's approval. One may not say Hashem's name without need! They saw among the people theft, and they did not heed the Shoftim (refer to 1:1:2:1). When Bo'az was appointed Shofet he enacted this, to fix in their hearts that Hashem oversees them and their Shalom, to the point that Hashem, who is called Shalom, joins with Shalom Bein Adam l'Chavero. Also, this will arouse them to put Hashem in front of them at all times, also when speaking among themselves. Also the harvesters fulfilled the enactment, and replied "Yevarechecha Hashem."

Vilna Gaon: When two people go, Shechinah is among them if they engage in Torah. If not, the Shechinah departs, for they do improperly - "v'Lo Yir'eh Vecha Ervas Davar v'Shav me'Acharecha" (Devarim 23:15). He saw a Na'arah among them, and asked, is Hashem with you? Did you stumble, and the Shechinah departed?

Vilna Gaon: She is a proper, modest girl. Hashem should bless you with her, for you need a wife ¹ , and she is proper for you!