I have to admit to basically total ignorance of Ada. It's got a heritage around avionics-type stuff right, extreme low defect tolerance settings? Looks kinda like Pascal?
Is it something that a true polyglot hacker needs to know? It's got important, novel ideas or unique applications that aren't addressed well by other tools? I love learning languages, but there are so many you'll never learn them all well.
It's my daily driver and I think one of the reasons my company can build very complex and high integrity systems with little staff. It's got a lot of nifty features and is still being updated to integrate more. I saw so many people very uninterested in hacking and programming, learning Ada and be so efficient with it so fast, with very few bugs, that there must be something there.
I'd say the driving principle is the language tries to have you write code that can be read easier, and is less concerned about helping you write millions lines of code per month. One example (when you get past the knee-jerk 'whoa it uses begin and end instead of braces') is generics where instantiation is mostly explicit (and thus can be painful to write) which helps reading, a lot. I'd downvote to hell any change to that (let the IDE/langserv generate the code for you, but please, generics are complex already).
The other driving principle is finding defects as soon as possible. So the compiler is harsh, there are lots of static checks. But it also helps you find defects at runtime as soon as possible. It can insert validity checks everywhere, if you can pay the runtime cost (hint: it's very rare you can't).
It has strong typing, very interesting typing features, no implicit conversion, most features you'd want in a modern language (tasking, OOP, generics, exceptions - erm...) and some that are more 'original' (contracts, quantifiers, if- and case-expressions, function arguments qualifiers in/out/in-out) and very nice union types (discriminated records).
Recently it has been extended to formal proof, with the SPARK language, which is Ada with some language features disabled and an automated proof environment (based on Why3 and SMT solvers), which is also its own interesting new tech, with interesting advances these last years (proof of floating point operations, memory ownership,...).
I think I could go on and on. But if you can spare one or two hours I'd just go to https://learn.adacore.com/courses/intro-to-ada/index.html and run the tutorial (all in the browser) and read a bit about all the features, and just ask questions downthread, I'll try to monitor it (like I don't already monitor obsessively all my HN comments...).
Is it something that a true polyglot hacker needs to know? It's got important, novel ideas or unique applications that aren't addressed well by other tools? I love learning languages, but there are so many you'll never learn them all well.