Many organizations have a class tree defined on an ItemType that includes custom forms for the classes. In this case, users are generally trained to add the new item and then select the Classification / Type control on the form first so that they can be presented with the correct class specific form before they start filling in metadata. This approach doesn’t feel natural. Users should be prompted immediately with the class picker when they decide to add a new item. This is exactly what the Razorleaf Class Picker solution does.
The download includes a package and instructions for implementing.