Maybe I have been lucky, or that the practice is more common in certain countries or eco systems? Java has been a very productive language for me, and the code has been far from the forced pattern usage that I have read horror stories about.
Depending on how much memory is used by the Thread stack (presumably 1M-512K by default, allegedly 128K with Alpine base images) that's your 1G-500M heap space usage improvement right off the bat.
The migration from JDK17 to JDK21 was uneventful in production. The only issue is limited monitoring as a thread dump will not show most virtual threads and the micrometer metrics will not even collect the total number of active virtual threads. It's supposed to work better in JDK24.
The Spring Framework directly supports virtual threads with "spring.threads.virtual.enabled=true" but I haven't tried it to comment.