VR Zone has some info about the SSD caching of Intel's Z68 chipset, you can read it over here.
Intel plans to officially launch Z68 Express chipset on May 18th but you will be able to see reviews online from 12th onwards. Of course, those who can't wait for the official launch can already purchase the Gigabyte Z68X-UD7-B3 board from the retail market, first available in Taiwan and then the rest of the world in the coming weeks. Other brands like ASUS and ASRock are set to hit the retail next. Those enthusiasts hoping they can overclock their Sandy Bridge better on Z68 than the P67 will probably be disappointed but there is one important feature of Z68 that matters, and that is the SSD caching.