So, here are what I would say are the big add on's with upgrading to 8.x and specifically 8.5. The first is scalability enhancments. The capacity of Unity Connection increases to 20,000 users per cluster and 250 ports per server (up from 10k and 144 in 7.x). The second is the addition of Single Inbox or Unified Messaging capabilities for Unity Connection 8.5. So, with 7.x you could do voicemail only and/or Integrated Messaging. With 8.5, you can enable Unified Messaging with any mix of Exchange 2003, 2007, and/or 2010 and you can enable voicemail only, Integrated Messaging, or Unified messaging features on a user by user basis...so this is very flexible. The architecture for UM with Unity Connection is much different than that of Unity so it is de-coupled in terms of dependencies on backend systems such as Active Directory and Exchange. The last is support for virtualization (i.e., UC on UCS). Of course, there are other enhancements but these are the big 3.
What I have seen on 8.5 thus far with clients is several bugs which affect failover and are relatively interrelated. Otherwise, you'd just have to do a bug scrub to identify any other common issues.
If you are looking to justify the upgrade, my advice would be to stay on 7.1 for a while longer UNLESS you specifically need one of the enhancements noted above. 8.5 was officially released in December but didn't really come onto market (i.e., shipping arrivals) until February and is currently at SU1 (i.e., 8.5.1 ES16) and some of the failover bugs are being fixed in a currently unreleased ES20. 8.6 has also been released for BETA trial customers. So, it is advantageous (IMO) to let Cisco incorporate some bug fixes and mature this code and then consider upgrading possibly this summer or later this year...unless you are pressed to fill one of the gaps as I stated before. I still think that 7.1(3b)SU2 is the most reliable (i.e., predictively stable) release of Unity Connection at this time.
Hailey
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