Have this on a pretty fresh 3.6.1. site (only few pages) for a couple of weeks and wondered why it takes 5-8 seconds for any page to load. Started to disable plugins one by one (as recommended) and found out it is this plugin.
Disabled, enabled, disabled, enabled etc. very reproducible and 100% sure it is this plugin.
When disabled pages take 1-2 seconds to load.
When enabled pages take 5-8 seconds to load.
I am talking about any page on the site, not just the page that has the contact form.
In case it matters. I am running the Virtue theme and the following additional plugins:
- GA Google Analytics
- Responsive Lightbox
- Simple Facebook Plugin
- Wordfence Security
- WP Native Dashboard
- Contact Form (by you)
- Captcha (by you)