In the codebase here we use 'jQuery' instead of '$'.
Ditto. If you pull in multiple plugins or additional frameworks (for some reason, we mix YUI with jquery), the $() notation can become broken, and you have to explicitly call jQuery().
Unless you put all your code in a big closure to make a correct $ in function scope:
(function ($)
{
}) (jQuery);
The article mentions that "the heat map does miss out on things like shift and caps. ex. in perl with the dollar sign. ($)".
Yeah, but the $ is shown as frequently-pressed in the Perl heatmap, so that must not be what he means.