In the past 30 days, Gmail has successfully tagged 8712 spams with a mere handful of false positives (which have now been flagged) and only three false negatives. I'm happy that this is good enough for me—as of now I will no longer review the spam folder.
If you email me and get no response at all and think you should have got a response, this may be a result of your message being flagged as spam. In that case, feel free to follow the advice in the Contact tab of this blog.