Well, the main problem with civil unions is that they create a series of complications that would not exist with a simple marriage. They just make things more difficult, rather than less. There is no point in them other than to satisfy some fundamentalist's psychological need to be considered in some way "better" than homosexuals. The fundies are still in tears over the sodomy laws being revoked, guys. The governor of Virginia recently signed something that had no purpose other than to specifically exclude homosexuals from worker protections. I'm sorry, but I really can't see anything behind this discrimination other than the same, old bigotry.
Really, not being able to get married through the same channels as heterosexual couples doesn't really bother me much, in and of itself. What bothers me is the spite and bigotry behind it. It's an insult, and I take exception to it. What, is your relationship with your spouse somehow so much better than mine that yours deserves a special name and set of privileges? Hand me that in person, and you'll get a dent in your head. Supposed "equivalents" to marriage only further complicate things, and most couples can't afford the legal counsel needed to sort out the legal complications involved in living together and with raising a child.
Oh, and the whole case against gay adoption is rooted in bigotry as well. The basic argument is that we make poor parents, nevermind that every study that has ever been conducted shows that, in spite of poorer average economic conditions, our kids tend to grow to be more well-adjusted and successful than those of heterosexual couples and are not the least bit more likely to be homosexual. What's the justification for discriminating, then? Spite. Nothing in it but spite.
Personally, I wouldn't trust myself to raise a kid because I've got an anger management problem, have zero leadership qualities, and procrastinate horribly, but this doesn't have a single thing to do with the sexual orientation of myself or my partner. Perhaps I wouldn't make the world's most wonderful parent, but there are millions of gay couples who would do wonderfully. Why screw them over, then? Spite? I can't think of another reason when having parents of the same sex actually seems to put kids at an advantage.