For the first question, the answer is probably the same for everyone, no? For reading, it's obviously kanji: remembering shape, readings, irregular usages; telling apart similar-looking ones. Especially in the beginning, they create an enormous additional cognitive strain compared to other languages, slowing you down and making you tired. In listening, it's keeping up with pronunciation speed and resolving short words with many homonyms (where you might not yet even know the correct homonym).
As for my personal goals:
- Read Japanese websites (pick up interesting news and technological developments, find game mods that are not covered on English sites etc).
- Cliché as it may be, watch anime without being distracted by subtitles (and without resorting to - usually horrible - English dubs).
- Be exposed to grammar and expressions that are completely different to the all-too-similar Western languages that I already know. Come to see meaning in what was previously no more than line noise.
- Train my patience and perseverance; have an intellectual challenge that's unrelated to work.
However, I'm not aiming to be able to write the language (by keyboard or by hand) or speak it.
Some questions for you, too: what will the survey be used for, that is, what will it impact? (since I don't think there's much more that can be done to make e.g. kanji learning easier)
Also, will the results of the survey be available to the public, and if yes, when and where?