Dunno - I think “Rustacean” sounds fine. Whereas “Pythonista” makes me think of Starbucks and hipsters (not necessarily a bad thing, but still), with “Rustacean”... I think of some solitary crab-like creature lurking in gloomy depths (literally, a “low level”)... robust, with a sturdy hard shell... content to exist without drawing a lot of attention to itself, but nevertheless a bit mysterious, intriguing.

Really, it’s a better analogy for Rust programs than programmers themselves, but associations don’t have to be exact. I see it as very much positive and cool.