For those of you that need a 256GB mSATA drive, you can add Crucial to the list of suppliers. Micron announced production in a press release back in April and they are finally shipping.
In fact, I bought one directly from Crucial at http://www.crucial.com/store/partspecs.aspx?IMODULE=CT256M4SSD3. The CT256M4SSD3 is a SATA III mSATA drive that already getting high marks from some of the reviewers.
See the review at http://thessdreview.com/our-reviews/micron-c400-256gb-6gbps-msata-ssd-review/ for details on the storage device. I am looking forward to upgrading a Samsung Series 9 notebook with it. See the review I did back in March on the 13.3” Samsung NP900X3B.