These are nice but it's funny how they fall short:
1: you can't combine attr() and calc() - calc(attr(data-count) + 10) <-- nope
2: how would you count down from an arbitrary number of child elements? you need to set the total via counter-reset... and, no you can't do content-reset: foo attr(data-count)
Heads-up for those with a penchant for ignoring the small print... IE9 RC will replace IE8... iow, there's no obvious way to install them side-by-side. As if anyone would really want to do that /sarcasm.