Looking at these comments (141 at the time of this post) the answer looks to be: No.

I have small business clients, Google's reCAPTCHA is our best option. They aren't willing to pay for some obscure, and expensive one-off solution that might work. They just want the spam to stop. I fill out reCAPTCHAs every god damned day because I work on the web. Asking "normal" users to fill out a handful each year isn't asking that much.

Maybe for your startup "rolling your own" makes sense, but not for small biz.