Antenna House, Inc has released XSL Formatter 4.2 for Mac, Linux, and Windows. This tool converts XSL-FO files to PDF. Version 4.2 adds support for Unicode 5.0, surrogate pairs, pair kernings and ligatures for European languages JIS X 0213:2004, Devanagari, PDF1.7, and PDF/A, and PDF Forms.
The "lite" version costs $300 and up, but is limited to 300 pages per document and doesn't support right-to-left languages. Prices for the uncrippled version start around $1250. Support costs more.