Be Not Defeated by the Rain, there was recently posted an excellent article by one of the top Taijiquan masters in the world, Chen Xiao Wang. Below in an excerpt. The full article may be read here.
The Five Levels of Skill
by Chen Xiao Wang translated by Tan Lee-Peng, Ph.D.
Learning taijiquan is in principle similar to educating oneself; progressing from primary to university level, where one gradually gathers more and more knowledge. Without the foundation from primary and secondary education, one will not be able to follow the courses at university level. To learn taijiquan one has to begin from the elementary and gradually progress to the advanced stage, level by level in a systematic manner. If one goes against this principle thinking he could take a quick way out, he will not succeed. The whole progress of learning taijiquan, from the beginning to achieving success consists of five stages or five levels of martial/combat skill (kung fu). There are objective standards for each level of kung fu. The highest is achieved in the fifth level.
The standard and martial skill requirements for each level of kung fu will be described in the following sections. It is hoped that with these, the many taijiquan enthusiasts all over the world will be able to 'assess' on their own their current level of attainment. They will then know what they need to learn next and advance further step-by-step.