Sonnet measured read performance for three manufacturers' 600X (90MB/sec) CF cards in the Qio, connected to a MacBook Pro:
Lexar Professional 600X...86MB/sec
Transcend 600X...............71MB/sec
SanDisk Extreme Pro........61MB/sec
This issue is now resolved. The Panasonic P2 driver included with Qio software version 1.2.3 and later is 64-bit compatible. Installing Qio 1.3.2 or later adds P2 support to systems running OS X in 64-bit mode, including Mavericks (10.9) and Yosemite (10.10)