We use Sitemesh, but I'm not a fan.
We use the apply-decorator function almost exclusively to wrap one of our standard page layouts around the unique content of each page. I believe this is best done with JSP tag files because they are built into each container and are part of the JSP specification.
I did not profile it, but, without the need, reassembled all the server pages to find sitemesh tags and perform rewriting, it always bothered me too.
source share