I'm a firm believer of not going overboard on the first Christmas you spend with your sweetheart. We all see stories and advertisements with couples getting engaged on Christmas Eve or Christmas Day; images of a tiny box with a ring in a stocking or under the tree. I've always stuck to the "TIS The Season" principle: TIS meaning "Take It Slow." Very often I would find myself swept up in the spirit of Christmas to the point where it would cause emotional and rational blindness. You begin overlooking the other person's shortcomings or issues that could turn out to be major issues later on. So I've learned to not make those types of gestures or gifts around Christmas.
Marriages and commitments are a different matter. I went through my genealogy database this morning and realized that there are many of my family members and ancestors who were married on Christmas Eve or Christmas Day. It makes perfect sense especially if the happy couple had traveled to be with family. It seems like a no brainer since there is an "instant reception" built right in with a Christmas Eve or Christmas Day dinner. As long as it didn't detract from the real reason for the season and celebration.
Another common marriage date seems to be New Year's Eve. Not only does it still qualify the happy taxpayers for married status at the end of the year, but again it is already "instant party time."