@Akeskin: We've not yet opened a case still. However there is no typo. We have adopted the 15.1 code pretty early due to some policy saying "you must not use firmware that is going to be EoE" - that was before Juniper decided to extend 12.3 support by one year...
I mentioned it in another thread - we still had the problems when we moved our test equipment from R4 to R5. As in the past R5 often was considered to be the first "mature" version of a new train I have some hope that things will become better now that the version overall has become recommended.
Just as a note also EX8200 NSSU is broken in the 15.1 code and leaves you with the XREs plus half the SREs updated but an error "access denied" appeares and so the other SREs do not upgrade even if you reboot them manually.. Plain software add with whole VC reboot works.
I cannot tell if this also applies to other models as I only tested NSSU for the 82's.
It is not very relevant to this topic here but similar behavior happened with our QFX5100 where I did the NSSU from the recent 14.1X53-D35 to the latest D40 interim release and after the NSSU OSPF was not working anymore. A reboot of the overall still working (checked via console) VC fixed this.. OSPF was in init state and not able to peer with the linked Cisco 6509's, while the links worked, according to LACP+LLDP. Also pinging the L3 interfaces worked. Restarting the routing process did not help. I just avoid NSSU whereever I can and only try it if it worked for my test equipment...