In my own experience, it's a solid but outdatedly old-school code editor, but it shines spectacularly in text processing.

I always tend to use other editors as my daily driver (TextMate, Atom, VSCode, whatever the new flavor is), but I always keep BBEDit around and updated for this reason. Eventually I am going to need to open an enormous CSV or logfile and do things to it and BBEdit is there for me. It happily opens the thing where other apps scream and choke and die, and it has great text processing tools to do things with that data.

Another thing that's not my reason for liking it but is very real is it's incredible Macness. Unsurprisingly given its 30+ year history on the platform, it's an extremely well behaved Mac application that adheres very cleanly to Mac user expectations of behavior. Doesn't matter that much to me personally, but you'll find a lot of the old-school "fondly reminiscing about Mac SE/30s" types really appreciate that it just feels more like a Mac application than probably even a lot of the built in MacOS applications these days.