I brought it into an aging ~12-year-old system to add a bit of SPA-like functionality to some pages. It works wonderfully with those classic MVC-style web sites.
I can highly recommend it for giving older, jQuery-era sites a new lease of life. I dropped in the CDN built into the view files, tweaked some of the controllers to return content outside of their usual template layouts based on a hx-request header, and I was away.
Didn't have to mess with bundlers and compilers. It was refreshing!