XML Tools team has released the XSLT Profiler Add-in for VS 2008 - a quick and reliable performance analysis profiler tool that assists in the development and debugging of XSLT documents. The XSLT Profiler Add-in for VS 2008 allows developers to measure, evaluate, and target performance-related problems in XSLT code by creating detailed XSLT performance reports. The XSLT Profiler includes a wealth of useful hints for XSL and XSLT style sheet optimizations, which are essential for XSLT-based applications that demand maximum performance.

read the announcement at Microsoft XML Team's WebLog