I think what's most interesting is not that this works well for common languages, but it seems to be useful for languages that don't exist yet. If you want _some_ highlighting for your SQL variant, or your language that borrows many common idioms, or just sloppy code that's close enough to the target language, this could be useful.
I don't use them as coding agents, but they can be very useful for things like text transformation, summarizing, or text extraction.
That said, if you have a subscription to a paid model already, you're not necessarily winning out on anything except perhaps privacy, which isn't nothing.