I've used TrackJS in the past - they have context on the user session surrounding front-end exceptions, e.g. what the user clicked on beforehand. Is a video replay really that much more useful?
In my opinion yes -- being able to actually see the user going through the app before they clicked on the thing that made an error can make a huge difference. Sentry's breadcrumbs are similar, but they don't provide enough context. An actual session recording provide all the context.