Civil unions, I feel, are a nice middle ground. Those in favor of gay marriage get what they want and those who don't want the word marriage, generally having a religious connotation, used get what they want. I don't like the idea of blanketing the issue so one side must give in to the whims of the other. I understand the unlikeliness of this being done, but I think it'd be nice reach a middle ground that is legally not a double standard and respects the views of the opposition.
Civil unions, while of middle ground on a legal basis, are not consistent with the historical context of marriage. While we have gradually come to see marriage as a religious act, it is far more likely to have been a social/political construct created in order to establish monogamous relationships in the ancient world, regardless of the faiths involved. Evidence of this goes all the way back to the ancient Greeks. Marriage, in its fundamental form, is a political, not religious, act. To deny homosexual couples access to this act is a principle repugnant to the concept of "equal treatment under the law."
No middle ground is necessary. No word change-ups are needed. Gay marriage simply needs to be an accepted, legal norm. It's not a matter of semantics. It's a matter of ethics.