Thanks!
I totally agree, personally I want more hierarchy; but user testing with milestones was pretty rough. Vistimo proper (https://www.vistimo.com) is less slick-looking, but has milestones and story-mapping and bugs and enhancements and all kinds of hierarchical organization tools. Most users I've tested with have found Vistimo Quotes' approach easier to pick up and use on existing projects, even if it's less powerful at expressing the full richness of the work.
Re: the long running calculations, I will take a look, but it's possibly just a traffic jam. There are a few more "test" simulations running simultaneously than usual this morning.