I think the new approach is better.  

First, it is the approach used in the official quantities documentation.  So anyone looking 

Second, it is the approach used in our own code.  So if someone looks at how something is done in our code or one of our tests, they will see the same thing.

Third, for something like quantities where there are dozens of possible variables, and the variables needed could change (someone could easily change their mind about whether they want to use seconds or milliseconds, for example).  Dealing with a large number of imports like that quickly becomes unmanageable in a larger file.  So the example doesn't scale well, and someone trying to take the example on expand on it will quickly end up with a mess.

All of our numpy imports work this way, so unless we want to switch the numpy examples also (which is a problem since practically every numpy example on the web uses this approach), the user will need to understand this approach anyway.