Once again, a hacker news commenter's idea of what in browser javascript performance is like is ridiculously 15 years out of date.

It's 2014 now. Your iphone is 10 times faster than your 1998 pentium 2. Even with the JS vm penalty.

Unless you're zipping 70mb files, there's no chance you're overwhelming anyone's browser.

The usecase for this is the same you'd have for any desktop application: A handy "binary file format" library. Data portability wins.