I played XI from NA launch til the day the servers got shut down and I have made tons of JP friends through parties. One thing that seperates their parties from ours is I have WAY more fun in them then I do with NA players. 90% of the time I am talking to myself while partying or just mindlessly mashing away at mobs, in JP parties they do crazy stuff, talk alot even though I understand none of it andits a friendly atmosphere instead of felling as if my party member daydream of snapping my neck the whole time.
BUT I have partied with my share of "bad apples" they are wild, uncooperative, even when the other JP players talk to them they agro mobs that were of no threat to the party then leave when we wipe. So its about 70/30 JP players are nicer when you get to know them but once you piss them off your on their shit list for life!