I just tried your plugin on a new blog (still under construction) and tapped into a severe mistake.
I have to explain my setup first, to make you understand the problem I found.
The blog poqueira.com is a three language site (English, Spanish, German)
Further every language is connected to its own database!
Installing the plugin on all 3 versions I got a constant redirect from the English to the Spanish version with the cached page presented.
I could not even log in to the English version to switch it off, was always redirected to the Spanish login. Had to delete the plugin via ftp.
You should think in an update, though I doubt there are many webmasters using my described system - only a SEO-manic like me might use this kind of set up.