Reports are largely a wash with speed, on average it seems like people are having their computers perform very ever so slightly faster on benchmarks.
Here are my before/after results:
Mid 2012 15 inch 9,1 MBP (non retina display, but with higher than standard resolution matte display)
2.3 GHz i7, 512 MB GeForce GT650M, 16GB 1600 MHz RAM, 2 TB spinning HDD:
Before today's supplemental update was installed: 3360 Single Core/11510 Multicore.
After today's supplemental update was installed: 3430 Single Core/11527 Multicore.
Mid 2012 13 inch 9,2 MBP (Retina displays didn't exist then for the 13 inch models)
2.5 GHz i5, Intel HD Graphics 4000 w/ 1.5GB shared VRAM, 10GB 1600 MHz RAM, 500 GB spinning HDD.
Before today's supplemental update was installed: 2796 Single Core/5582 Multicore.
After today's supplemental update was installed: 2856 Single Core/5223 Multicore.