At first, I was a little apprehensive to having to become familiar with yet another language, but I was really pleased to find how similar XML is HTML and how easy it is to interpret the tags.
It seems to me that most of the rub with working with XML is become familiar with the particular schema that you are presently working with. Some of the comfort of learning a language like Python or Ruby is that it is fairly monolithic and that most things that you do in one project can be done in much the same way as another. It seems to me that this is less the case in XML, but then again, I’m not sure how much work will be done with the form boxes on an editor vs actually tagging elements by hand.
As an aside, I was pleasantly surprised to see the “Rose” poem used as an example in the above link. Benjamin Britten set it to music in one of the movements of the wonderful Serenade for tenor, Horn and Strings. I think it would be interesting to see the differences in the metadata used to describe the poem as a poem and the poem set to music as part of a larger work.