I distribute an app that uses JSP. Users edit the JSP to customize it for
their environment. At the moment, we just call plain Java objects within the
JSP, but users get confused when they have to work around the Java snippets.
So we've got the classic how-to-separate-code-from-presentation problem.

We could use Velocity or FreeMarker to insert dynamic data into easy-to-edit
html templates. Most of our competitors, though, output XML and then have
the users do CSS or XSLT to generate the actual html.

Does anyone have insights on what the easiest approach is for your average
user? I have no experience with XSLT, but it strikes me as much harder to
handle than a FreeMarker-style template. On the other hand, XML is really
convenient in lots of situations.

Also, does anyone have insight into performance issues? Some of our
customers have really, really heavy traffic (many, many page views per
second), so page generation speed matters. My gut says that server-side XSLT
transformation has a lot of overhead, but I have no data to back this up.