We usually ONLY travel to WDW in January. Though the weather can get very chilly (this year, one morning, it was 38 degrees!). We are from Michigan so I can handle the cold, but, 38 degrees at Disney is COLD! Pack accordingly. Attractions are often closed for refurb in January also. It seems that almost every January (except for this past January - woo hoo!), Splash Mtn. is closed for refurb. Keep that in mind when planning. When making ADR's, you still will have the same struggle getting certain reservations such as BOG and CRT. But, keep trying and you eventually should get the restaurant/time that you want. To us, January is a gem and I hope people don't catch on how nice and un-crowded it is there!
I am a bit worried about the Pro-Bowl ruining the low crowds factor this year. We shall see...