Excellent plugin, very simple to configure and works great. I used this to insert the Subscribe2 form into a pop-up using its shortcode [subscribe2], and it functions smoothly. Can add HTML to style text, limit the pop-up from showing up within a set time limit etc.
For mobile devices, just adjust the width to about 40% so that the 'X' will show up on any size screen, allowing the pop-up to be closed easily.
The only annoyance of the plugin is the in-your-face promotion of the premium version, otherwise it's a nifty tool.
Ok the tool might be usefull, I didn't find what I was looking for so it was unrelevant for me, but nothing bores me more than download a plugin and being assaulted by ads bright colours, and encouragement to buy the premium version everytime it's possible. When you download this plugin, it only miss one thing, the blinking typo in your dashboard.