My qualm with this app is for a Linux user you can already build a system like that to yourself by simply using telnet and typing the HTTP directly down the pipe. The bonus is that you get to memorize all the protocol messages that way too.
The abstraction is provide better UX. Anyone will have to write stuff over telnet to provide chained requests, variables, assertions, etc. Once you do that, you basically get a reimplementation of hurl.
Curl is a good tool to familiarize yourself with, but I've written test with curl and bash it is very cumbersome this is another level of awesomeness for that. If all you are going to do is connect to a server with some json, then curl is ok, I agree that nc/telnet/socat might be a bit extreme.
Hurl is not enough for some of the tests I want to write, i.e. testing sending a 50MB file, or dynamic content.
