I've been using this WP pluging now for several weeks on some sites that I use no SEO on... although I'm essentially an SEO guy, I drive traffic to some of my sites using a variety of means, on of them being PPC. For that reason, I could care less about bounce rate as to how it affects my SEO.
It has certainly helped with revenue on these sites and I have actually implemented another pop up plugin that is goes off simultaneous with this one to an offer that is similar to the ones I present initially and I am very pleased with the results.
This is good for more than SEO bounce rate; you can almost force your visitor to reconsider buying if they have not made a decision in your favor initially.
Don't just think SEO/Bounce Rate here, don't think a discounted offer, expand your thinking and see if you have an ancillary offer that you can sell to your visitor that will pay you as well as your initial offer; that is working very well for me.