I have some Bullseye red anodized aluminum pulleys. Not bad but noisy. I switched to inexpensive Tacx sealed bearing pulleys, plain ol' Delrin, quieter and really helped reduce some annoying drivetrain friction in my old Suntour RD with sintered bearings. Those things were terrible compared with Shimano Centeron.
I guarantee, after Ronan McLaughlin's recent Everesting record, more people are gonna take a serious look at those oversized pulleys. Although I suspect the real key, besides his engine, was the terrain and climate.