I don't need to get up to speed in a weekend. It's the speed that I'm getting up to that matters. Of course there is a limit to this principle, I grant you that.
What matters as well is how readable other people's code is, or even my own code after not touching it for a year. And I mean readable for someone as proficient in the language as the original author. This aspect sometimes seems underappreciated by proponents of "powerful/expressive" languages.
I like Go for this reason. It has more noise (err) than I'd like, but when I look at most Go code, I find it relatively easy to follow and modify. There's no other language I've used that achieves this so consistently.
That being said, Go was fun to learn, and taught me that deployment does have to be as painful as it's been in Java for so many years. But I encourage people to also spend some time with Rust, as it has made a very different set of choices. For me the type and generics system are the best I've ever used and I wish I had access to them in Java.
Then you should spend some time with OCaml and Haskell. :)