[jliechti1]

I think the bigger problem in Mandarin is the large number of homophones (at least, for me).

To help speakers of non-tonal languages understand how difficult it is to differentiate between tones, after you get used to hearing them - it is as apparent as the differences between "rebel" as in "to rebel" and "rebel" as in "He's a rebel."

So hearing is not as difficult as might you think. However, in line with what cageface said, I think it is easier to hear the difference, than to reproduce it yourself.

[seanmcdirmid]

Tones are easy, you just have to speak naturally and they'll naturally fall out, you don't even have to think about it. Most learned of Chinese overcompensate on tones, they would be better to forget the, and just pick that aspect of Chinese up from practice.