Depends on how you define Marriage. If you mean in the religious sort shown by the people in Devies post, then i am against it. Marriage was meant to be the holy matrimony between two people (man and woman) gay marriage would contradict this.
Now don't get me wrong, if you mean marriage as in the binding of two people until death or however (as in non-religious) then I would support them 100%. I just personally don't see the point in changing the term 'Civil Partnership' Just to 'Marriage' Just for the sake of it, when really its just a word, the commitments are exactly the same.