Okay, I was never keen on pairing in MLP (since nearly all characters are female), so in order to stay objective, I shall not treat this as pairings but FRIENDLY relations... with the exception of Spiek and Rarity, of course.
Lets beging with the concept, shall we? Undeniably this piece is very befitting Christmas, the feeling of joy and togetherness practiculry beaming from the pic. The cousy background and various activities play a great part in the work as a whole, leaving a feel of holidays, even though they're already in the past (until December, at elast).
Of course originality of such piece is hard to determine as, in its time, there were countless Christmas-theme works flooding the fandom; most were "postcard", but the idea was similar - ponies doing various activities together. With the general rule that few things are original these days, it's hard to make a concept that hadn't been used earlier, especially on the topic as popular as holidays. Still, the warmth of the house this one presents does have a sort of uniqueness to it.
The technique is very nicely picked, giving an impression of this being done by hand at first glance, which furthers that special feeling Christmas is supposed to bring. Simple and yet detailed, this piece stays true to its source material in more ways then one, creating a beautiful whole, peaceful and nice.
The impact is undoubtfully this piece's strongest merit - the inclusion of various ponies, even background ones, really brings forward the feeling of togetherness, which Christmas is all about. The activities, scattered across the pic, which usually implements at least two characters plays on that emotion even deeper, making it nearly jump out of the frame. And yet you managed to keep it gentle, mixed with other feelings that are usually represented by the tiniest of details that one can easily miss at first glance. The overall joy that's shown in this piece sneaks up on the viewer, almost forcing a smile. Granted, that's what MLP as a whole does, but you've managed to amplify that experience nicely.
Overall it's a very nicely done work; to some it may seem childish and yet it plays a great homeage to the source material, managing to fulfil it's goal easily through a simple use to characters and activities most of us are very familiar with. Simple... and yet touching.