Christmas at DLR is absolutely worth it!

Like Molly said, it is incredible - no matter what your faith or spiritual/religious beliefs are, people agree that it is just beautiful at DLR during that time of year and everyone should experience it. If I had a choice to go to DLR only one time in a year, for one day only, or one time after not having been there for several years, it would be during the holiday season. It is absolutely my favorite time to be there.
I guess one way to describe it would be that DLR, in general, has a certain 'magical/fantasy-like' quality that everyone who loves DLR feels and recognizes when they are there. So take that feeling, amp it up and multiply it by 1000 and you have DLR during Christmastime.
First of all, there is the Winter Castle, which seems to sparkle and glow incandescently throughout the park. At certain times during each night, the 'icicles' on the Castle illuminate and there is a little light show that extends from there, all the way up Main Street, to the huge Christmas tree. Then the 'snow' (suds, basically) falls on Main Street.
Then, there are the ride overlays: there is the jaw-droppingly beautiful IASW Holiday, which, in the daytime is mildly impressive, but at night, draws crowds from all corners of both parks to gaze at its stunning, colorful facade. Inside the ride, everything has been transformed for the season, and the usual IASW song has been mixed in with holiday tunes. The smells of peppermint and some sort of pine waft through the air. Of course, there is also the wonderful Haunted Mansion Holiday, which makes its first appearance in late September and lasts until January. Every year there is a new, fresh gingerbread 'house' sitting on the table in the banquet scene (last year it was a coffin), and a snowdrift Hidden Mickey on the ballroom floor. As you pass by this scene, you get a strong whiff of gingerbread.
Add to those things the special holiday food items such as cookies and peppermint pot cake and cider (who doesn't love the gingerbread men 'with ears' cookies and the peppermint goodies?), the aromas, the colors, the lights, the decorations - there are miles of garland strung aroud the parks, and no fewer than 700 Christmas trees of all sizes scattered about DLR. They are everywhere - in all the shops, in all the restaurants, in all the DLR hotels, throughout DTD, in store window displays, and of course, in the 2 parks. ToonTown and A Bug's Land have their own unique decorations, and New Orleans Square has his its own kind of Mardi Gras-flavored adornments. Plus, Santa can be found at the Reindeer Roundup in DL, and at all 3 hotels (at the GCH, he is a PhotoPass opportunity). Christmas carolers stroll through DLR, and they perform (they take requests) every night in the huge GCH lobby by the tree. Guitar and piano players provide constant holiday background music in the GCH when the carolers are not singing.
Speaking of music, let me also not forget the sounds of the season at DLR, especially in DL. As you make your way from land to land, you will notice that the Christmas songs change style, depending on where you are. In Adventureland, you may hear a steel drum/calyspo-influenced version of "Deck the Halls," for example, and as you move into Frontierland, you will notice the Yuletide tunes (playing as ambient noise) are now performed with banjos or in country-western style. Expectedly, in NOS, you can hear "Jingle Bells" done up in a jazzy, French Quarter kind of way.
So have I convinced you that it is worth it yet?