With Chameleon RC1 and a DSDT.aml edited to correctly inject the parameters for 8600M GT, the XPS M1530 worked perfectly, giving an openGL viewer score of 125~1600
With Chameleon RC2 (Graphics Enabler =y) and the DSDT.aml no longer injecting anything for the 8600M GT, the performance in OpenGL Viewer is cut by more than half, 125~700
With Chameleon RC2 (Graphics Enabler =n) and the DSDT.aml edited to correctly inject the parameters for 8600M GT, the performance in OpenGL Viewer is normal again at 125~1600