From the time I was 5, through age 25, my family went every year during the Christmas to New Years week. I have also been back, during non holiday times
It is extremly decorative and festive that time of year. I think that the experience is incredible and it is one of the best memorable times we had.
But of course everyone is different. And the one thing I think is fair to say is that it is INCREDIBLY crowded there. For some people, it's understandably too much. Waits for rides can be hours, to make dining reservations, you better make them months in advance. Also, the weather while usually ok, can be hit or miss. I have been there during both warm and cold.
We stayed at Monorail hotels which really cut down travel times to the parks, buses often can be so full, you have to wait for awhile on very crowded ones.