This may explain some of the problems I've seen with uplinks that need the DHCP client, up to at least Junos 12.1X44-D20.3.
If I make changes to the configuration and commit them, especially in [system services dhcp] but not limited to that area, often the provider uplink will go away (no more IP address on the interface). I then need to do one of three things to get it running again - the connection won't recover by itself.
o commit a disable on the interface, and then enable it again (I've now set up a conditional cron job from a nearby linux job to do a 'commit confirmed 1' that disables the interface if it can't reach the outside world).
o pull the cable for a few seconds
o or reboot the whole device.
This makes remote management very tricky. I think this is unbelievably bad, as if the whole typical situation never got tested. If Juniper thinks these kind of things are not a problem I'm not going to use them anymore.