I have two YN560 (originals, not I, II or III) and two YN568 II. I can't rave enough about them, especially for the price. Only problem that I have with them is the YN568 II's I have suffer from the battery door problem, but they have replaced this since Oct 2013 I believe.
I use old RF-602 for manual triggers when needed, but usually use the Canon 90ex flash as a commander for ETTL, HSS, and remote power control and it all works beautifully. Never had a misfire or any kind of overheating issues.