My response to a Twitter challenge by @thomasfuchs. I <3 modules and dig microlibs, but I think that consistent cross-browser support is more easily obtained by using a modular/buildable library instead of a bunch of independent microlibs.
Explore the performance cost of pre DOM-load reflow caused by some feature tests. I created a special build of has.js that runs all 177 unminified tests upfront before DOM load. This is an extreme case and executes 3-8x more tests than most projects will use.