We've installed quite a few of these (over 12 at least) and are installing new sites almost biweekly. We have installed numerous 50+ seat IP Offices, and a few with full functioning call centers (with CCC), as well as Multisite networked IP Offices, IP Hardphones, IP Softphones, etc.
One thing that really determines how successfull the product works is by the competency of the programmer and installers. Also since it is still relatively new, may intergrator lack experience and are installing misconfigured systems.
The great thing is that it is simple to learn and customize, so if you have a custom application or need, there is almost always a way to come up with a solution to it and sometimes you may even have a few alteratives.
We have even done a migration of an office of 60+ users from a Definity to an IP Office, and thanks to the ability to use 64XX sets on the IP Office and the Intuity interface on the Voicemail Pro, we did this on a Friday evening with very little user training and great satification as we programmed the system to mimic their Definity.
PS. 1.3 did help with some issues we had, such as dial-by-name, and ON/OFF buttons. Thank you,
Frank Mirecki