The interface is great, it's very simple but still allows for customization of everything you need (including customizing your own logo).
There was nothing I didn't like about this product! It has been an incredibly helpful tool in our marketing efforts at work - especially when we're looking into running contests or sweepstake promotions with clients who are not tech savvy themselves :) We've had some really good results from using GEOtokO as well -- both through word-of mouth advertising & online ads placed by us directly via Google Adwords/Adsense etc., plus social media promotion too : ).