My first impression, as beginner, let's say i come into game by "accident", clicking a link or a banner on a web site, is that this game take alot of time. You must be online for upgrading hero by fight. It is a game for the players who have time to spend on web surfing.
Also needed alot of battle to gain experience.
In Firefox are some problems. After a while (10 min) the browser blocks. That is a big problem, considering big number of Firefox user arround the world.
Also needed a help assistant. And, of course, multiple language interface.