I've tried many platforms already (Still using them for other projects) I started with Zenkit for a new venture and it is working wonders! Many features that differentiate them from the others.
I see great potential in this product, better than Trello. But must fix few issues: speed, drop-outs, data loss due to drop-outs, keyboard shortcuts (for web version). I'm a heavy user of products of this kind, I've been using the web version for ~ a year, except for the issues mentioned, love it!