Similar thing happened when the Quick Cache plugin guys brought out a pro version, but I was fortunate enough to see that there had been problems and didn't upgrade until the problems had been sorted.

Quick Cache problems were sorted pretty quickly but lots of low score and negative comments had been posted by then - damage done and the plugin rating fell like a stone.

"...because the amount of users and environments using the stable version are far greater than the number participating in the beta period."

That makes sense and with a plugin as complicated as " iThemes Security" testing must be pretty complex, but if your site is the one that's broken... you don't see things in such a clear light.

I don't use this plugin but thanks for the heads up Jeff and I'm sure that this one will get a good conversation going in the comments.