New version of sfCaptchaPlugin is added to Symfony repository:
http://trac.symfony-project.com/wiki/sfCaptchaPlugin
It contains small but quite important fix to remove zero from captcha alphabet as it does not fit newer JpGraph version as was reported by some developers.
By reviewing the code I noticed that there is used dynamical route for sf_captcha and I remembered that this other developer told me that dynamical routes are not really good solution – as they are not caching. So if you want to speed up captcha appereance you’ll have to remove dynamical route and simply add it to your main routing.yml. Of course, this wont have much effect on small sites but for heavy-loaded ones this can be quite helpfull. By the way, the same situation is for sfGuardPlugin and the other ones symfony native plugins.