Our family went January 4-8, 2005. MK crowds on Wednesday, Jan. 5 were low in the morning with 10 to 15 minute waits for Peter Pan's Flight, Pirates of the Caribbean, Jungle Cruise and Haunted Mansion. Crowd levels became moderate in the afternoon with 20 to 30 minute waits. As evening approached, crowd levels increased substantially as a result of the EMH night, and we left the park by 5:30 PM.
Attendance on Thursday, January 6 and Friday, January 7 was also low in the morning and moderate in the afternoon. The attendance on Thursday evening, January 6 was high because of the SpectroMagic Light Parade, but we were able to walk on most rides without any wait during the parade. Saturday, January 8 became very crowded in the afternoon with 50 to 60 minute waits for the most popular attractions. We used FastPass to avoid the longer wait times.
This year, the Disney Marathon ends on Sunday, January 8, so you should see a decrease in crowds by Monday or Tuesday. Have a great time.