Here is a quote I received today in my forums relating to gl-captcha v1.0
It's still great that you made this CAPTCHA.
In the span of the last 5 days it has stopped 106 attempts, twice they were followed by attempts to login with the user they thought they created.
So I would say it is at least worth a try if you want another tool to help combat spam bots. There are ways to circumvent CAPTCHAs but I have not heard of any issues so far with gl-captcha.