I encourage people to check out the free-form answers in the user survey for answers to the question that opens the thread.
My subjective summary would be that the most commonly-cited pain points are documentation, and the tools (with some people complaining in particular about the documentation of the tools). Other things people mention less frequently include the syntax and the lack of libraries.
I think this thread currently on the front page is also a good illustration of the sort of problems people have with the tools.