In a proper managed environment (whatever that may mean...), this could be useful as a means for continuous integration. Maybe not worth all the hassle, but maybe there's a usecase where this would be a beloved silver bullet.
Hot code reloading (ala Erlang) is often used in embedded devices for control code where restarting is very expensive. Mostly telco and networking devices.
we use it in prod to instrument code to check up on some internal data, say, from the database, when some forensic analysis is needed
We use something similar in some of the web crawlers in my company, we dynamically load the module that selects the data from a web page so that if something (website and/or requirement) changes we can just swap the module without downtime.