I find this course very well done. There are few like this one which goes so nicely in the details.
And as everybody knows the devil 
is in the details.
The problem with pinyin is that it was primarily designed by chinese for chinese people. And if we read pinyin as if it were english we make a lot of errors. Professor Xu explains very well how english people would naturally speak and what kind of mistakes they can do.
The only slight problem I have is that I am french and not english and we have differents problems with pinyin. The ü and l sounds are very common in french and is not a problem for french people speaking chinese. On the other hand the y and w are less common in french and for us their use in pinyin is unclear.
Firstly I explains how we pronounce these two letters in french :
The w has two pronounciations in some cases it is pronounced like a v for instance wagon (carriage) the wa is pronounced exactly the same as the va de vague (wave) and in some other cases it is pronounced ou, watt has exactly the same pronounciation as ouate (cotton).
The y is pronounced i the ry of rythme (rhythm) is the same as the ri of rime (rhyme). yi is also pronounced the i, yi of yiddish is the same as the i of idée (idea).
So when Xu loashi says do not miss to add the y before i I feel hen ganga because in french yi and i is exactly the same.
The w is also unclear for me. I would pronounce 5 wu as who in english. But when I hear chinese speakers say Wuhan it sounds to me like ou, not exactly the same as 5.
