But I think I remember that lvalue subs are considered experimental. I super searched here, but didn't become much wiser.

I think lvalue subs have been deemed experimental for quite a long time, but they've been there and working for all this time. As far as your question is concerned: most times you don't really need them, but in a few cases they provide what indeed seems to be the most natural and straightforward syntax for certain tasks. So it's indeed a nice feature to have. granted, it would be better if that "experimental" tag could be eliminated...

PS: at least as of 5.8.6 the "experimental" mark is still there, see 'perldoc perlsub'.