It's as formulaic as any other romantic comedy, and at no point were my sides in any danger of splitting. Wilson, however (whose character has more depth than Vaughn's), seems like a surprisingly impressive actor.
Christopher Walken does what he does best, projecting instant gravitas and power tinged with potential menace. Isla Fisher (who I remember from Home & Away!) is fairly one-dimensional, though Rachel McAdams is a good match with Wilson. (The unrated version is seven minutes longer.)