tlpeter,
I love the IP Office as well. I work on both systems, as well as all other classic AVAYA systems. I find that when I work on the IP Office with VM Pro there really isn't much that I cant do software wise. I can meet every customer need. On the other hand, the "Partner Version" is not the IP Office. I wish it would be more a step forward. The only benefits I can see so far is the availability to do remote access through VPN and I don't have to worry about lines and voicemail inhibiting my total station count. I just took a look at the voicemail auto attendant configuration. No submenus, no option to have a selector code go directy to a voicemail box, and no direct extension transfer (I may be wrong on that).
A step forward in my opinion would be Partner phones on an IP Office with Vm Pro, SCN, IP Phones, and a larger max extension count. That way when my Partner Customers are maxed out at 48 extensions I have an upgrade path for them where they don't have to purchase all new phones. Such as the Partner/Magix or how about Merlin Plus/System 25/System 75.