I'd call XML easier than HTML.

But, you make one false assumption. I can say I've "learned English" because I can use it fully in an everyday environment. I gave him an everyday environment/code to make, and he wasn't able to. Thus, I'll say he hasn't "learned JavaScript." He may be "learning JavaScript," but he hasn't "learned." I would say I have "learned JavaScript," but not "mastered." I know there's tons of stuff I'm not familiar with... even some basic things. (For example, I can get confused with search() sometimes.)

Meh, I was being technical anyway - learnt is just another way of saying you've gained knowledge in ...

Either way, XML is useful, so it's really worth learning. It's not as strict as XHTML, nor is it as hard to learn as HTML (which, by the way, is brutal when you really want to validate and look good at the same time).