What rights are denied to couples under a civil union/domestic partnership?

I know I've been ignorant, but until now I had no idea that these people were denied basic rights of marriage. I only thought they objected to the wordage.
Which rights specifically are being denied? (I heard something about emergency room visitation, but that's about it.)

1. Same sex couples even the ones that are registered as a domestic couple or civil union cannot adopt each other's children, or a child together
2. Even though your registered domestic partner is eligible to share your medical benefits, you pay income taxes on it. For example if your registered domestic partner that was covered by your insurance went to the doc and insurance paid out 1500$, you have to pay income tax on that 1500 where as married couples do not have to do that. And thats only with the few corps that offer domestic partner benefits. Most companies do not.
3. Registered domestic couples in my state atleast are NOT the automatic legal next of kin as a married couple would be. This plays into the hospital thing that you are talking about. By HIPAA laws medical personelle can only release information about you to your legal next of kin or power of atty. If you are not conscious to tell them it is ok to tell your registered domestic partner, they cannot. So even though your partnership is registered, they have no right to your medical info unless they can provide proof of a seperate power of atty document.

Those are just the ones that I know