5.0: any improvement concerning memory management?

Is there any improvement in the latest J2SE 5.0 concerning memory management? Setting the maximum memeory via "-Xmx" is just not flexible enough for todays server applications. Does 5.0 return unused memory back to the operating system?
[243 byte] By [MartinHilpert] at [2007-9-30 18:12:29]
# 1
GC ergonomics has some differences http://java.sun.com/j2se/1.5.0/docs/guide/vm/gc-ergonomics.html
Martin3 at 2007-7-6 18:44:31 > top of Java-index,Administration Tools,Sun Connection...