In case anyone is curious, I just got a new 15" rmbp. Disk tests on the blackmagic disk test were around 730 mb/s read/write for the esata SSD. This is the 512 gb model.
Nice results, but depending on the application, sequential read/write speeds aren't as important as small file random read/write speeds, so that would be a more interesting test. I'm not sure of the best application to test that on a Mac. Xbench is one that is free and it would be interesting to see a comparison between the old and new rMBP for different block sizes, plus for reference a comparison with a cMBP with a fast SATA-III SSD like a Samsung 840 Pro.