Obviously Technical Analysis alone won't help you to a successful trade. It has to be a combination with other factors such as Risk management and those you have mentioned
I have been using TA for sometime now since late march this year (it's the time I decided to do serious trading and I have) and i have made something like 32% profit though i haven't been consistently trading daily yet. I think i would have made more if I was trading full time.
Quite very effective if you are willing to taking small profits per trade and not be so greedy.