Sigma Photo Pro 4.0 was announced alongside the launch of the Sigma SD15 SLR and DP1x / DP2s compacts, and includes several desirable new features. Most notably, processing performance should be significantly improved on modern multi-core computers, as Photo Pro 4.0 supports multi-core processing for the first time. There's also a new image processing algorithm, and an additional noise reduction function applicable when shooting Raw files at ISO 400 or greater.
Sigma Photo Pro v4.0 is available for download immediately in both Windows and Macintosh versions, from the software download pages for the SD14, DP1, and DP2 cameras. (It's also available on the DP2s' download page, but is actually included in the box with that camera.)
Sigma Photo Pro 4 requires either Windows XP SP2, Windows Vista 32-bit, Windows 7 32-bit, or Mac OS X v10.4+ operating systems, along with a minimum of 512MB RAM, 1GB available hard disk space, and a 1,024 x 768 pixel, 16-bit or greater display. The software is a free download for Sigma customers.