1 - At a high level, I ask myself if the language is pushing me towards the pit of success or the put of failure. More concretely I ask myself "given the class of problems appropriate for this language, are good abstractions easier to create than bad abstractions?". If so, I have a positive reaction. If the reverse is true, and it's easier to make bad abstractions (think early Java where functions were not first class), then I have a negative reaction.

2 - If the language is trying to sell you on a certain paradigm? If so, is there a good escape hatch? This at least means a good FFI like that found in Erlang, but also within the language, OCaml's refs which allow you to write imperative code are a great example. Elm is a language that does this badly, 0.19 removed FFIs and the language is much reduced for it.

3. Is packaging a first class consideration of the language? This is one of the places where say, Rust shines and Python really suffers. I'm going to need packages and if managing them is hard I'm going to get mad.

4. Does the language free me from some class of problems? Big positive.

Some languages I've liked: Common Lisp, C, OCaml, Haskell, Python2, Javascript ES5, Racket, Erlang

Some languages I've disliked: Java5 and earlier, C++, Go, Python3, PHP circa 1999

such a good question! I don't think I've ever had a particularly strong guttural reaction to a language, but I'm definitively biased and either see things that I quite like or dislike in a new language I see.

As I think about why those are I think one of the biggest reasons is familiarity, it's easy to get comfortable doing one thing and it truly sucks to feel like you don't know anything again (I think somebody called this the curse of knowledge? Idk).

Lately I've been intentionally the unknown, or, those languages that I'd look at and be like, "but why!?", for example, why would I want to learn or only use recursion when a for/while has worked for pretty much my whole career? or, following the same functional languages traits, why immutable data? seems like a step backwards?

But the thing is that people, quite likely smarter than me, or at least, a lot more familiar with challenges that I'm not familiar with, came up with solutions that diverge from what I know... and I want to know why! Why they came with immutable data or recursion or a language that pretty much everything is a list (LISP)... and the answers are quite surprising and at the same time I feel that joy of discovery that has almost been erased by years in the industry.

So when you come across a language that you have strong feelings/opinions about, wearing the shoes of the people using it might be quite enlightening and enjoyable.

While I say this, I'm a complete hypocrite because I won't give such courtesy to OOP... but hey, none of us are perfect ;-)

Easy to answer for me personally. I don't specifically care about the syntax family of the language, but I found Haskell (and functional Scala) to be pretty much unreadable. I have no problems with Lisp dialects or ML, or C-family or a lot of others... but Haskell with its heavy use of symbols instead of words... nope. I seem to need a certain 'instant hook' from which I can learn. If there are only symbols it won't work. Maybe that's also why I always found reading and writing math much harder than grasping the concepts. (I studied Computer Science, not real Math ;))

I had this very experience today! I was looking at some code for markdown parsers (I'm trying to build one in Hare), and I stumbled upon a Nim example. I don't know what it was, but just seeing how complex the author made what seemed like a simple struct to me filled me with dread. I'm sure if I took the time to understand the language it would make sense, but Nim is just one of those languages you need a second glance to understand if you're not already familiar with it.