With that kind of system, you can use a plain ordinary HTML editor to do everything from writing templates to writing content and it is sweet. With all of the semantically-oriented elements in HTML5 the code is nice.
Text-based templating still rules the roost and I think performance is a big part of it. I've tried it in both the Python and Java ecosystems and found that you lose at least a factor of ten in performance if you use X-Soup. In the case of live page generation that is both a latency and a throughput problem, in the case of a static page generator, however, it is not so bad.