Here's what we learned from Brooklyn: Italian-American hunks are like Irish girl kryptonite. Although the novel ends with their relationship teetering on the brink of disaster, Eilis and Tony's whirlwind romance defines Eilis' life in Brooklyn and helps her grow into a strong woman.
In other words, Tony is the coolest Italian plumber since Mario. Sorry, Luigi.
First off, it must be noted that Tony is an incredibly loving boyfriend. He's actually a pretty emotional guy in general: he gets powerfully affected by movies, for example, which makes Eilis "feel an immense tenderness for him and [wonder] if she would ever see a side of him that was disagreeable" (3.442). This carries over to their relationship as well, and he's constantly making it clear how much he digs Eilis—which is a lot. This loving nature starts taking a dark turn, however, after he starts with the incessant "I love you's" and wedding talk.
Tony's eagerness to make a commitment stifles Eilis. She really likes him—she might even love him—but this is her first real relationship, and she's still getting a hang of things. Plus, marriage is so final and Eilis still feels too young to limit her future potential. She even wonders if there's something fundamentally wrong with their relationship, saying that his "delight seemed to come with a shadow, and she wondered [...] if she herself [...] was the shadow and nothing else" (3.470).
Despite these reservations, Eilis agrees to marry Tony before visiting Ireland. We have two minds about this. On one hand, it seems like Eilis is succumbing to Tony's pressure simply because she's afraid that she'll lose him. On the other, she does seem to actually want to marry him—think back to when she "spotted someone at the next table checking out her wedding ring" and "smiled to herself" (3.949). Ultimately, however, this is a question without an easy answer, and the truth probably lies somewhere in-between.
Needless to say, we still feel bad for Tony about the tomfoolery that goes down between Eilis and Jim. Their relationship certainly had problems, true, but Eilis owes it to the dude to be straight with him. Still, Eilis also wonders during their trip if Tony would be cool with her working part-time after they had kids, which points to non Jim-related problems in their future. Even if they do divorce, however, we're confident that Eilis will eventually treasure the time she spent with good old Tony.