Similarly argued, icon fonts are cool but have x-browser rendering issues, dependence on webkit for accurate anti-aliasing (currently), require sticking to a 32x32 grid, and altogether lead to a massive headache for nimble development. In most cases, especially for new products and low traffic, it's premature optimization. Github's speakerdeck gives a great rundown of their experience:

https://speakerdeck.com/u/jonrohan/p/say-hello-to-octicons

And note, this is Github, who actually has reason to optimize for >2MM users, saying the process was is too complex and tedious.