Hi, we have been running it from March starting with R80 and despite couple of problems that we had (i.e. backups - now all resolved, revisions was not too big concern for us and easy to maintain, MLS? if you meant log server then the only issue was inability to upgrade MLM from R80 to R80.10, fresh install only option) I would strongly recommend upgrading to R80.10. For us it was a lifesaver in many aspects - ability to upgrade VSX boxes to 64bit kernel on VS unlocking memory limitations of 32bit kernel, concurrent administrator option, GUI experience in general is much better.
Some small things to keep in mind:
MDS restore time is considerably longer (for us it went from ~half an hour on R77.30 to well over 1hr in R80.10). Depends on your disaster recovery requirements.
Far away administrator experience can be very flaky - we have administrators sitting other side of the world from MDS with 180ms latency between client and server and they are unable to use SmartDashboard. It's too slow. The only solution is to get local terminal server for them.
Log search seem to slow down over time and we need to reboot MLM from time to time to get it going again. Haven't had time to dig into it and/or raise an SR, but seems some memory leak..
Good luck!
Kaspars