I tend to agree with javery. The UI needs polish. Your homepage could use some as well; as it is now there isn't anything that wows me and I wouldn't use this over AgileZen (although I currently do not even use that, the only Kanban system I am using is physical and I use Pivotal Tracker for everything else because it's free and awesome).

UI and design are more important then you think. I don't care about features unless they are so disruptive and innovative that I just have to have them. Saying you have X, Y, & Z isn't really appealing to me. Competitors can easily add features but they can't easily build a better overall experience. Experience is a balance of UI, UX, general design aesthetic, and yes features. The keyword there is balance.

It seems you are currently focused on features and none of the other stuff.

Are you working with a good designer on this project or is it just developers?