Out of over 3200 domestic partnerships registered with the Washington State government, only 3 have been dissolved? That's so much better than the (almost) 50% divorce rate here. Who said gay marriage would weaken marriage??
That's pretty impressive, but you have to consider that it is a lot more socially acceptable for heterosexual couples to get married than homosexual couples, so gay couples would probably think about it for a long time before deciding to "tie the knot". Also, since it has only been 9 months since the domestic partnership bill was passed, it might be that not enough time has passed for the rate of dissolves to equal the rate of divorces. While I doubt the rate of dissolves will ever get that low, I think that, in time, it will indeed increase.