I think the biggest thing I'm worried about from my end is I just work with so much C and C++ I can't attempt to do programming that takes away from being productive. I don't have the hours for it. I don't recall the Rusts docs yelling out to me, "Don't forget! C FFI bindings can be generated!" But at least Steve was able to point out some libs to me that would help with my work.
I'm OK with a small productivity hit because learning something new will always entail that, but the long term benefits need to be there. I'm almost always more worried about shipping than I am about anything technical.
That being said I think I can see some benefits over the horizon. In C and C++ land, there are a lot of people who don't use std or boost for one reason or another, and I've worked in circles where I had exposure to that type of programming. Honestly, just the fact that I might be able to rely on Rust's libraries OOTB could be a productivity gain right there.
I have the "Hello, World!" rust app on my workstation, so I've given it a small try. I'd be curious to see how other powerful concepts like threading work in Rust, but that's reading I've got to do.
It's difficult trying to sort out threading concerns from Lua, another language I use frequently, since the most common distributions aren't thread-safe without some work. I'd be interested in seeing what a Rust + Lua software integration could look like, since that might be a successor to the C work I do now.