Overall I like how easy it was to just turn on this plugin, make quotes, and toss in some shortcodes in content on a website I am building.
However, I thought I would mention that you have at least one issue cause by assuming $_POST always has a specific index.
On line 121 of perfect_quotes.php, be sure to add a quick
at the start of your conditions. I think there might be other instances where other warnings appear, but this is the only one I repeatedly run into as I am creating content.