Just had my first failure of a 600ex-rt. While getting my setup shots for a big group session, I was turning off one of my Speedlites when I noticed a little resistance in the switch. I did not apply much pressure, but I felt a mild snap. Sure enough, the switch had just broken, and the unit is now on its way to CPS. (I guess you could say the toast dropped butter side up, because the switch left the speedlite powered on, meaning I could go ahead an use it. Only way to power off though was by removing the batteries.)
I have several of the 600's, so I can't be sure exactly when I bought it, but it was within the past 18 months. I know that I did drop one (landed on its side, not an end) while walking fast from about 4' onto a grass covered (but hard) field. That was a year ago, but it never had an apparent issue. I don't know if this is the one with the broken switch, but other than this incident, I have not had a single problem with any of them.
So, as I'm getting more location work (thankfully), I'm wondering if other owners of the 600ex-rt have comments about its ruggedness and reliability.
Also--does anybody actually use the "Lock" position of the power switch?