Whilst I'm sure this is clever - I guess I'll never understand the obsession with micro DOM optimisations. When, ever, are we severely held back by the 'speed' of our selectors? It just doesn't happen!
There are some web apps out there that are sluggish as hell if one doesn't have the latest beefy machine. Gmail or Google Doc running on old hardwere are examples of this. "Mobile web" apps are very sensitive to DOM manipulation performance too.
I'm not saying that all sluggish performance in web apps is caused by inefficient DOM manipulations, but having a DRY and efficient way to express DOM manipulations could help a lot in that regard =D
On mobile devices, we were hitting significant performance barriers from DOM and class manipulation. YMMV but it seems DOM performance is an issue on non-beefy boxes.
