I've used Nim just a bit on Windows/MingW (I'm from python world). The very short program I made (about 200 lines, mostly math stuff, no framework imports) compiles in 2-3 seconds. It's already too long for me to iterate (it's not a rant against Nim, it's just that it's too long for my way of working; the language is nice and gives good results). Also note that Nim compiles fast, it's the compile-to-native compilation step that takes 90% of the time.