As others noted, I'd revert to curl commands for sharing with others (or for performance-sensitive tasks like downloads or quick-and-dirty load generation) but this may become my go-to HTTP CLI for personal use -- if only because it looks like won't need to look at the man page every time I want to do much more than a basic curl -X <METHOD> <URL>. (But maybe that says more about me than curl/httpie.)
One neat feature to add would be a mode that accepts the curl syntax (or at least the common parts of it), that way all the curl examples and "Copy as curl" tools work with httpie as well.
Conversely, an option that accepts httpie syntax and outputs the corresponding curl command might be convenient as well. (But I guess at that point maybe httpie devolves into a command-line parser + pretty-printer that wraps around curl, but that may not be all bad either.)