[westiseast]

Yes and no - achieving real fluency after a certain age is very very hard, near impossible. Writing chinese by hand is exceptionally difficult too. Typing characters using pinyin inputs is significantly easier. Speaking in simple conversations like Mark has is really not that hard - again, not to undermine him specifically, but rather to dispel the idea that this is some superhuman achievement. he's at at moderate level in spoken Chinese, I would expect any learner who has the same teachers and a Chinese wife and family to achieve a similar level in that amount of time.