quick question
 

Is there an advantage or use for having /usr on it's own partition?

Yes. This is the place that stores almost all the commands and programs. It is good to have its own partition not sharing with root as it changes in size, files.. etc majority of the time.

I always think of it this way, if the directory is going to grow or change in size more often than lets say your /etc directory, which will rarely ever grow in size, it usually needs its own partition.

Ah, okay...