Ordinarily I am very forgiving of Canon. They have a business to run and their profits help create products that I want.
But, the abandonment of the 580EXII was very unprofessional in my opinion. This was a strobe marketed to and used by professionals (which I am not). To release the 600 EX and transmitter without releasing a backward compatible receiver was an unconscionable disservice to the many professionals who invested in multiple 580s.
In addition, though, it was probably very bad business on their part as I am sure, even as I write this, Yongnuo and others are reverse engineering the strobe and transmitter and preparing a receiver for the 580EX (At least I hope they are doing that).