I have used the Yongnuo RF-602 triggers on my EOS-M, they work fine, but they are just dumb triggers. Slightly disappointed that the sync speed is still 1/200 though. However I love that it has the full Canon RT functionality in the menu.
JD, don't get the triggers, sell your 580EX II's and upgrade to the 600EX-RT's, you will some day anyway so do it now while you can still get a great price for the 580's, you won't regret the move and using them on your 5D MkIII is a dream of simplicity.
I also got the free 90EX, it is a great optical trigger too, I emailed B&H and pointed out the error they had made, they emailed back to keep the 90EX with their compliments. Wonderful customer service.