It is the best way to add captcha protection to your custom modules. TinCaptcha is very easy in use and allows to place image wherever you want.

I don't understand what's going on with this component. I installed it, made the changes as directed but it seems to make no difference to my contact form whatsoever, other than to put a pretty but non-functioning captcha form at the bottom of it. My form only allows you to submit when all fields are filled in, including the captcha form input. However with the rest of the form filled in it makes no difference if you put in an incorrect version of the captcha image or even just 1 letter or number - the form submits regardless and says 'Thank you for your email'. Seems that the captcha is entirely superfluous and dosn't do what it's supposed to. Maybe I'm missing something but there's no trobleshooting guide for this problem and the author's website no longer exists.

The author did not make it clear that this CAPTCHA engine requires modification to Joomla core files to be applied to the default contact form.

Finally, after the email exchange with the author, I found out how to modify those code. I think the author should include that link to the forum post in the extension description.

Though this is a good extension, I think modifying core files is not good.

Installed and applied to the default contact form without any problems, the best part unlike some other capthca solutions the edited forms were already available. Avoiding the need to insert code yourself and easy to find where the chagnes had been made.

I don't like to start out with criticism, but there isn't much to complain about with this component/plugin, so I'll get it over with so I can talk about the good parts.
Con: Be comfortable with editing the core code - download, edit and upload files. But that is the only drawback to this great resource!
The install went fine - it was a little troubling to install a component then not see it in the component menu. **I should have really read the forum postings linked to in the description before I installed it.
I tested the form entering the correct captcha, then the wrong captcha. When you put in the wrong values, it sends you to a page stating that it was not entered correctly and on paging back, all my info was still stored in the form - yay! I also tested the captcha refresh and it worked fine. The only thing I haven't tried yet is to change the fonts and used it on a VirtueMart form. Tomorrow maybe!
So, with a few manual edits supplied by the creator, this worked great for me.
Thanks!

This is a really nice extension, which does exactly do what it claims to do. A nice way to add a Captcha to your site wherever you want. I've referenced this in an article that I wrote for the upcomming Joomla! magazin and I'm using it in my own extensions.