Coming from a Romance language background in general and a Spanish background specifically, I've taken great joy in the Japanese pronounciation and verb/grammar structure systems. Maybe it's just me, but it simply sounds beautiful rolling off the tongue. Not like English, where everything kinda sounds blocky and disorganized in comparison.
I've never been good with vocabulary in any language, so that's just a personal thing. And the kanji system just kinda goes without saying. My Japanese professor tells me to sit down with a pen and paper and tells me to write each kanji 100 times or something, and instead I go home and try and figure out a personal system for forming more complicated kanji based off the ones I know. I've learned from doing a lot of the latter that you're basically stuck with that pen and paper.

As for things like particles, the only problem I have with them is when native Japanese speakers just sorta neglect them completely. To say the least, it requires some getting used to.

-- Gerardo