I love early January - anytime January 2 to right before MLK weekend. In my experience, the marathon just causes some minor traffic delays in the morning for two days - but otherwise its a "non-event" for non-runners. Crowds aren't super high; but I wouldn't call it super light, either. Weather is challenging to pack for - and you need to dress in layers - as it could be 40 degrees in the morning and 80 degrees at 4 pm and then 60 degrees by 6 pm. I often use a locker this time of year so I can change clothes/not have to carry stuff. Park hours are short (historically) - that is a disadvantage. I think folks underestimate how cold 50-70 degrees can feel at Disney - and LOTS of hats, scarves, gloves, sweatshirts are clearly purchased by the unprepared. When you are outside that much - and it's often still cool inside attractions/restaurants, too as they aren't well-heated - you can be cold. In one 5 day span - you can be dressed in T-shirt, sweatshirt, heavy jeans, light coat, hat, scarf, gloves mid-day - and two days later be in a T-shirt/shorts mid-day. January 2-4 you MIGHT catch the last of the Christmas decorations - or you might miss them. I have pictures of Main Street MK on the same trip with and without them. Anyway - for me - it's a great way to ease back into real-life after the holiday season - a bit of time at Disney!