I too have had more than my share of line breakage when using PowerPro, over the course of more than a dozen spools, all purchased at different times, from several different vendors. More than with any other braided line I've used. Perhaps this is due to a weakening of the line where it might get nicked slightly on a rock or something during retrieve, I don't know. But, if such slight nicks are going to so severely compromise the integrity of this "superline" that it parts the next time it is under the slightest tension, I think I'd rather use something else.
In my opinion, it's not enough to check the line prior to casting. When you have a fish on, the line is even more likely to get nicked up/weakened, and you risk breaking off before you even have reeled in the line to the point where you would be able to see the nick or abrasion.
As far as castability goes, I had little trouble with it on my setups, but when it did get tangled, it was not the easiest line in the world to work with. This alone was not enough to stop using the line,,,, it was more the breakoff issues.
All I can say is fishing the same lb test, under the same conditions, on the same rod/reel, I have not had a single breakoff, for any reason, using Fireline.
I seriously don't think anyone could logically chalk this up to operator error,,, perhaps just an inconsistency in the production of the line. Sometimes you get great line,, sometimes not so great. Sounds like Roccus has gotten some great line. I didn't.