Even though I had come across it before, I had a real revelation when I read David Hestenes short paper on it (from Bret Victor's website) http://worrydream.com/refs/Hestenes-ReformingTheMathematical... It is indeed beautiful to see how complex geometry and vector fields are connected via GA. I found especially revealing the relationship between electric and magnetic fields. I agree with the article that whatever its absolute merits, it would be a good way to teach new physicists. I have already ordered my copy of "Clifford Algebra to Geometric Calculus".

Whether it is actually more practical to do work in General Relativity or Quantum Mechanics, or indeed Quantum Field Theory etc., I'll have to leave for the experts in those fields. From an outsider's perspective, it is a delight to understand some of the connections between different disciplines in a more intuitive way.

In any case, I would imagine that GA is exceptionally useful for computer graphics and physical simulations.