I love that this makes social media sharing so easy and has a variety of styling options.

I like the ability to create a popup for my websites then track to see how often it was showed and used.

I like how easy it is to instantly start collecting emails from site visitors. We set up coupons to use for visitors coming from specific sites. For example - visitors from Google or a AdWords ad get 15% off. The analytics is nice. We can see where the visitors spend time and bounce prior to a purchase. You can set the different optimization levels to always improve conversion rate. The results are arranged very well. I also like how it shows the subscribers that have come via sumome.