The nim runtime overhead is very small. In my tests it was very easy to out perform the latest Node and Java runtimes with shorter, and still type safe, code.
I have some criticism for the language itself around personal preferences, such as "concepts need to be finished ASAP", "don't depend on libc" (Zig is doing a much better job here) and some syntax pet-peeves.
Nim needs to be more popular IMO. Well, the same goes for D too. Sigh.
1. Support for cyclic imports 2. Official WASM support. I know nlvm exists. But those are two separate runtimes to be managed for long time.
I was writing a compiler I remember where I hit the 5k LOC mark in Nim. And then the errors and stuff. It was a terrible experience putting all the types into one file, the functions into others etc etc. The DevExp is bad that way.
Other than that, I don't see much issues with Nim to be fair. Its quite a good language that ticks all boxes
Some problems are - vibe.d does not look nearly as performant or supported as, say, Drogon, which is what I was seriously considering using (I love the idea of using C++ with modern move semantics and coroutines to make async code easy).
I know and love Java and Node a lot - just want to try not using a VM for a bit :)