Seriously, what's so broken about X? Is it just a pain in the ass for developers to work with?
I taught myself X from scratch last year. I didn't find it hard at all. In fact, I found it a whole lot easier than either of the fancy modern GUI toolkits that I looked at first and tried to use to implement the project I was working on.
Out of desperation born of lack of progress over an extended period, I thought I'd take a look at X. And suddenly it became easy to get the interface to behave *exactly* the way I wanted instead in somebody else's idea of what I should want.
And the documentation was complete, correct, and easy to follow. I didn't have to keep asking people for help (often, with no resolution). In a word, both the documentation and the code for X are mature. Which I submit beats bleeding edge every time if you're trying to build something robust.