We also went this past january, Thursday was beautiful 70 degrees, no crowds...fri, sat , sun, poured rain, 40's wind chill in the 30's, the morning we left, the real temp was 38 degrees. It was miserable weather. plus the largest convention in orlando history, so everything was crowded.
This is an unusual experience, I'm from Florida, and 3 constant days of rain and cold don't happen too often.
My inlaws go every winter, either the week before or after MLK holiday,and before the Daytona 500, and they have always had pretty good weather and no crowds.
You just don't know about the weather. You just have to keep watching it.
But despite the weather, we had a great time both trips, I personally would rather go in the summer, I really hate any temps less than 70 degrees, but you wouldn't catch the inlaws there any other time!