I recommend you read again...
Most people on here agree: reg cleaners are to be used if you constantly install and uninstall software. Furthermore, you should always backup your registry before cleaning it, and if you're not sure what you're doing, don't clean it at all (at least until you learn more about the registry).
As for the difference in opinion regarding what software is "best", it's a matter of preference. Go ahead, ask what OS is best and see if you get just one answer. Most likely, there will be some people defending Windows, some defending OS X, and some defending various Linux distros.
So, to answer your question: "What do users at all levels of competency take away from this thread?" They get a neat list of pros and cons to reg cleaners, who should use them, and a number of different reg cleaners to try. However, users with little to no reading comprehension, get mad and write comments like yours.
EDIT: Fixed some spelling errors.