Works every time.

The ones that are impossible for my are the street signs, and after that all of the cultural ones (I see US captchas and when asked to select a sandwich or a recreational vehicle I'm doomed to not complete them).

An interesting side effect of failing a captcha is that to Google this looks like proof the captcha is working, that you're likely to be a bot, and that they should definitely give you the hard captchas.

As such, if you cannot complete a captcha the chances increase that you must now complete multiple difficult captchas.

The audio captcha is delightfully simpler though it does take a moment longer to complete.