Yeah, I like how Project Mu is cheaper than SRF. It has a higher wet boiling point than Motul RBF600 for about the same price. I can't justify the SRF price.
I used to burn RBF600 brake fluid regularly on my old Evo on track so the Project Mu was a good upgrade. Those cars are much harder on brakes than the M3. The factory Brembos are way undersized for the application.
Edit: Looks like Project Mu G-Four's price is now higher. It used to be about $30-40 for a liter. At the current price, SRF is the better deal.