Working with XML files -
using all these tools like awk, shell scripting, sed everything would work
But IMHO
they are not maintainable,
quite difficult if you had to do some modification (just extend XPath or append something to the root element for example ),
will take more time for modification and testing.
In short, its not supported.
Instead there are wonderful perl modules available from CPAN.
Though, the initial time spent on learning and figuring out is more, its worth spending the time.
But for quick win cases, 1 time runs - all these awk/sed/shell scripting should be fine.
When the scripts that work on XML files need to be productionized or need to address a big set of file base, then they are not scalable way of doing them.