Having studied Wilber for 20+ years I can tell you he is a mixed bag. Some of his stuff is mind blowing, some does not hold up to scrutiny.

The Four Quadrant Model he developed is one such thing. At first I thought it was great, then after using it, realized it is problematic. But it did get me back to Kant who had a 'Three Worlds' model: objective, subjective, and intersubjective knowledge. This is much more useful from a philosophy point of view.

The other thing that is overlooked is his take on Modernism and Postmodernism 'flattening' knowledge to objective, or intersubjective worlds. This, I believe, is the most important idea he developed, and I wish was better known. It really sums up Postmodernism and the age we live in.

Unfortunately, Wilber hasn't aged well. He hasn't taken the best parts of his work and developed them. Instead, he has focused on spiritual evolution which is more religion than philosophy.