I was instructed by Zimbra Support to upgrade to 8.6 first instead of 8.7.x directly because the upgrade failed immediately with a direct jump from 8.0.9 to 8.7.x. In fact, 8.7.x is such a major upgrade that I felt it should have been released as 9.0 instead.
I also understand that Ubuntu has stopped the support for Ubuntu 12 and to avoid the instability of Zimbra 8.7.x (new patches are released every few weeks), I could move to Ubuntu 14 or 16 (still under Ubuntu support) with Zimbra 8.6 (very stable with no further patches) and be covered for a few years with a very stable and reliable Zimbra for my users.
Some of my frustration with 8.7.x is not just having to install the proxy (which is a major headache by itself), there are also the memcached to be installed, the HTTPS redirect requirement, even the Kernel of Ubuntu 12 has to be upgraded to at least version 3.11 as well. Not to mention that the full installation file is no longer available for download.
The need to download additional installation file ONLY during upgrading process that take hours to complete mean additional downtime of at least half a day for my email users. This is unacceptable to my management. In order to reduce this long downtime, I will also need to setup another Zimbra repository server just to hold these additional installation file in order to upgrade to 8.7.x. This come to the point that my management is seriously considering migrating out of Zimbra to Microsoft or Google email solution.