R. Johnson
Let me start off by saying I have been a professional wedding/portrait photographer for the past 21 years. I have been using Canon products the entire time. I started with the 540EZ, then the 550EX, 580EX, 580EXII and now the new 600EX-RT and 600EXII-RT. Not sure what Canon did to these new 600 versions but they just do not have the staying power of the older units. I need flashes to be fast and reliable. My 580EXII"s were/are die hard workhorses. I was shooting and event and ran one of my 580s to the point the front lens melted but it kept on firing and didnt miss a beat. My flashes are always connected to external battery packs so they can recycle quickly. At the beginning of the day, these new 600s are fine if you let them rest 15 or 20 seconds at least between firing. Thats the good....the bad is once you start needing them to fire every 3 or 4 seconds, they start to fail. The original 600s would go into overheat mode and just stop working. The new version two, just stops working. It typically takes 5 or 6 seconds to recycle with a fully charged pack and fresh batteries. These units are totally unreliable. If you are using them in manual, no problem, my issue is when I am using them in ETTL. Radio triggering also no issue. I really want to love these flashes but when I really need them in a critical situation, they constantly fail. If you are a hobbyist and just shoot occasionally, these are a nice option. If you need them to work no matter what, look elsewhere. I dread the day when my 580EX IIs finally die as Canon is no longer repairing them.