We absolutely love the train park in Scottsdale and frequent there a few times a month. It's always clean and the kids love the train and the miniature model train room.
The park is a five-star experience for sure; however, they do need to work on their efficiency for the holiday lights event. Fortunately we got there an hour before the train started and were able to get tickets without there being much of a line. The line to get on the train was a mile long already. When we were leaving, close to 730, there was a line into the parking lot for tickets and then a line around two buildings for the train. I don't know how long others had to wait but I imagine it was hours.
Plan ahead and you'll love the experience.