I actually think that _adding_ the concept of civil unions is okay, specifically because there are non-homosexual reasons for it. For example, it would be a nice device for old ladies who share a house to have a civil union if they have little or no family left. They can get this done now, but it's a huge legal hassle.
That's fine with me so long as it is not imposed by the Judiciary. I think gay marriage should be banned as a moral principle, but practically speaking I am to the point where I don't care what they do in Mass or California, but I do care if those states have it imposed on them by Courts because it portends it being done on all states by a federal court. Plus, I think that is an improper thing for the Courts to do. It is not their proper role to be deciding such things.