As a girl, I could honestly not care less about a ring. That is not to say that most girls don't care, many girls do care about rings very much and I can respect this. However, a small rock is merely symbolic, and in reality has very little to do with engagement.
On a similar topic, I would never accept a diamond engagement ring. The actual rock is practically worthless (they are only so expensive because DeBeers controls the entire diamond market and advertises them as a rarity), and there are still people dying in South Africa harvesting these worthless rocks!