If you are using a lot of XSL Transformations and have migrated to ASP.NET 2.0, then there are some significant preformance gains to be had by making a few simple code changes. The XslTransform class is now considered obsolete and has been replaced with XslCompiledTransform. This class on averages performs transformations four times faster than XslTransform. Basically it is supposed to be on par to using MSXML 4.0 directly.
It's syntax is roughly the same as using XslTransform. Unless you are using some of the more obscure parameters with XslTransform, you can pretty much do a straight refactor nad it should compile and work. If XSL performance has ever been an issue, I recommend making the change as soon as possible.
The link below contains detailed information on it from Microsoft's XML Team.
XslCompiledTransform
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