In general, solely using an icon instead of text (or a combination of the two) is poor from a usability standpoint. Within a mobile context, I can understand the general push towards more compact treatments, but an icon with three lines does not intrinsically have any definitive meaning. While the icon may be aesthetically pleasing, I always felt there were some more effective alternatives.
There's been some recent discussion and data generated related to this icon (1,2), some of which can obviously be debated, but I think it's safe to say it's not as ubiquitous as you may think.
Overall, I don't think the hidden drawer pattern (and the associated menu icon) are appropriate for the site when it's being used on a desktop. But, it's OK given the contents of it and understandable when the site seems to have been designed mobile first and responsive. I do think more time should be given to the final 'desktop' state for a lot of responsive designs these days, though.
[1] http://jxnblk.tumblr.com/post/82486816704/an-update-on-the-h... [2] http://exisweb.net/menu-eats-hamburger