I am genuinely interested in seeing this game, but I'm not really convinced yet.
For example, in the FAQ the interviewer asks what makes Icons different from a traditional deities framework, and then Tweet takes 3 long paragraphs to explain that basically, yeah, it's like a traditional deities framework. Various civilizations are (abstractly-speaking) rules by different Icons, and do geopolitical things in those Icons' names, but you can't actually fight the Icons and you don't really meet them, and some Icons don't like each other so their people tend to fight each other. You can use words like "dynamic tension" all you like; it doesn't make what you're saying anything more than "the followers of this god Icon are generally the enemies of that god Icon, so you can count on them not to get along."
The real problem is more general: Tweet emphasized over and over again that the point of the system is to get tailored to each particular group, in mechanics as well as setting. But how, exactly, does the system encourage that? Does it just leave out crucial setting details and tell me to "make this part up"? Because that's not helpful and it's not encouraging customization; it's just being incomplete. I can play 4e or Pathfinder and just replace anything I don't really like. What's more, it sounds like this Icon system is pretty hard-wired into the 13th Age setting. Well, that's not more customization, that's less. If my group thinks the deities in 4e are stupid, I can ignore them easily. But it sounds like if my group thinks these Icons are stupid, it would throw off a lot of what 13th Age has to offer if we threw them out. Who's encouraging more customization now?
Anyway, a system designed by these two designers will (at least) be very good, and a system 100% committed to gridless combat sounds good. I'm just not convinced, from this interview, that the system's gonna be any more implicitly customizable than any other system.