or $ = d3.selectAll; surely?

You also need to re-bind it to d3.

  $ = d3.selectAll.bind(d3);

Since `this` in the `selectAll` will refer to whatever is before the period. When we reassign to `$` in `$ = d3.selectAll`, we lose that. Silly, isn't it?

Demo: http://jsbin.com/guyisewexu/1/edit?js,console

From my perspective I would rather have $.select() instead of $() because it makes more clear what this function actually does.

Future maintainers will hate that.

Done as a global, then probably, yeah. If it's assigned at the beginning of a function as a local var, then used 5 or 6 times, probably no harm done.