First of all, I would like to thank you for realeasing the STIX fonts this year. In the last couple of months, I have been using them almost exclusively for several documents containing lots of mathematics.
There is one issue that has been troubling me: The fonts have the code page bits for east asian languages set (bits 17-21 in the .ulCodePageRange1 field of the OS/2 OpenType table). It seems that these cause the Windows PostScript printer driver (PSCRIPT5.DLL) to generate code that is not compatible with GhostScript (http://www.ghostscript.com/) and some printers. This was reproduced in Windows 7 and Windows XP. In both cases, the issue went away after changing the bits (and corresponding checksums) in the font files.
As east asian languages are not really covered by the STIX fonts, I would suggest to turn those bits off in future versions.