At its most complex, it can be horrible, yes. If somebody was mainly interested in complex cases, I doubt if they'd even think of using ABC (and I wouldn't recommend them to). There are some things I've typed up as ABC that would have been much more pleasantly done using standard notation. But then I'd have needed 2 different systems for handling my stuff, given that most of what I want is much easier as ABC.
"Given the facilities of only a pen \ paper \ straightedge" ... If I had manuscript paper handy I'd use it (and then type it up as ABC when I got home), if I only have the back of an envelope I use ABC rather than draw the 5 lines.
Standards ... "the nice things about standards is that there are so many to choose from". 2.2 is still draft, after 5 years ? I tried to get involved in one or two threads of that discussion, but retreated, baffled. Is there very much ABC out there that conforms to any standard other than its own ? I don't think I've seen much, but I may be behind the times.
I think Will's right about learning to read. The concepts are the same either way, but seeing them in pictures would probably be easier (for a majority of people), ABC's more of an abstraction. Not hard once you're familiar with the ideas, but probably an extra step if you're picking the ideas up in the first place.