We filed our first taxes as a married couple and were surprised that we owe money when we had always both gotten decent refunds from both federal and state. Now, I'm not saying this will happen to anyone else here, but I wish I'd thought about how changing my filing status would affect our refund, say, last year when we could have done something about our withholdings! But everyone seemed to have the sentiment that we'd get more back now that we were married. Not so, for us anyway. I also started a separate file to try "married, filing separately" and that was far worse for us.
So if you have TurboTax or similar, it might be worth playing around for an evening and creating a file with a joint return, plugging in your info to see how you'd fare next year (assuming your earnings will be about the same and tax laws are fairly similar) to get an estimate.
Sorry for the Debbie Downer post about icky taxes; we now return to your previously scheduled wedding planning fun!

Kristen and Bryan ~ 10-10-10
