I'm really fed up with mine, one new problem after another. No effective range in working conditions, add in a flash on the Mini and the other won't fire, test fire and it works, put the models in place and it won't, the Flex stops firing and has to be retrieved, turned off and reset
It's a dose ~ these things take the worst of the Canon system and make it ten times worse. It's seemingly a lottery for me if they chose to work correctly for brief periods.
I work on the move as a PJ ~ IMO, totally useless for a volatile active or impromptu sessions ~they need to be set up EVERYTIME ~ I've taken them off and returned to the Canon IR as it is more reliable ~ sorry to say.
I'll still hang on to them and continue to try them as they improve the firmware or issue a recall, they are useful in sunlight where the Canon IR is at its weakest but the variances in exposure are enhanced, ETTL is a bit like that, too much under too much over but usually pretty close, with the Mini/Flex extreme under or over exposure is, for me, still toooooo common.
I've already had replacements from PW tech support and I've made my own shield as PW won't give me one but to no avail ~ maybe I am a poor shield maker? Maybe it's all my own fault.
When my cheap Chinese TTL [for Canon] arrive I'll have more to say ~ but that probably won't be until mid 1Q 2010 at the earliest.