I'm not married myself, but I do have something to contribute. This actually has nothing to do with the wedding itself but the timing of it all.
I recommended to a friend of mine that she and her fiance get legally married this year despite planning a wedding for next year. Her fiance makes about $100k, which is solidly in the 25% bracket (close to the start of the 28% bracket actually assuming no traditional retirement account contributions). She on the other hand is a student making nothing.
By getting legally married this year, they will still end up in the 25% tax bracket but all of the money is taxed at a lower rate because the tax brackets are wider and they won't be as deep into the 25% bracket. I calculated the tax savings as several thousand dollars (don't remember the exact figures).
Of course, there are non financial considerations to take into account before doing this. Also, some couples will be subject to the "marriage penalty." But it can make sense for some couples.