It's extremely convenient on Belli. For example, I recently noted that it can be used there to directly implement a request for automatic vehicle HUD attachment and detachment (https://feedback.secondlife.com/feature-requests/p/assosciate-a-hud-with-a-vehicle-and-have-it-automatically-attach-detach)
A related feedback item was denied (https://feedback.secondlife.com/ldpw/p/add-avsitter-experience-by-codeviolet-to-all-premium-sandbox-regions) but because it's activated on the Belli estate, I'm not seeing why it shouldn't be on Mainland as well.
This experience really amounts to a protocol that, unfortunately, isn't available without it, and the relevant source code is all open source—but that source must be compiled with the experience, and the experience must be enabled Estate-wide to be useful for things like vehicles, as it is on Belli. (Of course a parcel can always block Estate experiences if desired.)