After live upgrade'ing to snv_57, i was unable to get network informations, normally obtained using internal DHCP server. In the system log file, i can see something like:

Sat Feb 17 11:06:18 unic /sbin/dhcpagent[1494]: [ID 91213 daemon.warning]
 configure_v4_lease: incorrect broadcast address 255.255.255.255 specified
 for nge0; ignoring
Sat Feb 17 11:06:18 unic /sbin/dhcpagent[1494]: [ID 94624 daemon.warning]
 checkaddr: expected peer address 192.168.1.255 on nge0, have 255.255.255.255

In fact, it seems an old bug was reintroduced while working on an other (related) CR. See bug report 6516629 for a detail description of the problem. Since it was already fixed in snv_58, and because there are other known issues with this build being unable to boot some systems i will stay with build 56, waiting for build 58.