NOTE: this is just from what I have heard... I hear Google especially does not like sites that use Zango gateway, and you might get punished on search results, but...haven't really seen any evidence.
Not for me, Google always crawled and indexed every page that had zango's gateway. And my SEO ranks didnt drop either.
You shoulden't have any problems with the Googlebot indexing your site because it simply ignores any javascript and it'll just read the HTML. As D-Block said though, you might find your rankings suffer and in the worst case your site could be labelled as malicious. I havent personally seen this yet with zango and i'm not sure how their software is categorized (spyware, adware?).
In my experience it won't affect Google results BUT it will slaughter your returning visitors stats. Worth it on some sites, and horrible on some!