Structural typing is really necessary in Typescript just because Javascript objects don't generally carry a class around (at least not if it's defined with the {} literal syntax). I find though, that now that I've used structural typing nominative typing is a lot more restrictive and I generally prefer the structural approach. It's especially nice with JSON objects coming from remote APIs.

It is a tradeoff though, there is one thing I tend to like better about nominative typing that isn't quite as easy with structural typing, and that's reflection. Sure, you can query about keys/fields in the instance itself, but you can't match it back to say a type annotation on a class very easily. Type guards (for things like overloads) can also be a bit weird to write, for instance you can't really do an "instanceof" because that information is lost at run time, so instead you write these functions that can return "T is Cat", and that function will check for something like if the instance has a "meow" function attached. Once you get used to it it's basically fine, but it can be a bit cumbersome sometimes.