Just a quick note to respond to Arthur - when I was setting up mobile-reportcard, limn was usable only because Dan was being supremely awesome and hand-holding me through a lot of stuff. There is absolutely no documentation, and I can't just read the code because I'm not familiar with Coco (and considering its stated goal to be closer to perl + lack of a community, it is not something I want to spend time on). Having it in Coco also means I can't really fix things when I run into bugs. Having to hand-write the config files was very painful, considering that it was JSON and there wasn't really any documentation. I later heard that there's YAML available, but that I did not know at that time because... there was no documentation. I personally found Limn a lot more painful than I thought it needed to be, with a bit of too-much-flexibility and over-configuration issues - everything seems possible but nothing seems easy. Adding a simple time series chart should not require as much fiddling as it requires now. If I were building a dashboard for personal use, Limn would definitely be off the cards.
Diedrik also started another thread about what Limn should be and should not be, and I think that is a much more important thing than language choice. I've still never understood if it was supposed to be a 'here is some data, make some nice graphs so we can track key metrics!' software for building reportcards and dashboards? Or is it a super-flexible data-warehouse kinda thing where you can explore data and make charts to figure out what is going on (aka excel on steroids)? I personally find that it tries to be the latter but we are using it to be the former and that sortof sucks. Having clarity on what the product should be will alleviate a lot of my pain points, I think.