I totally agree with KCFLHRC. I grew up with Nortel starting on Norstars, then Meridian 1 / CS1000, and finally BCM's with CS1000e etc. Since Avaya came on the scene, things have gone fron bad to very bad.
Most customers just require the ability to make and receive calls with the option for call diversion to an external number or voicemail etc. Avaya products are very complex and feature rich with functions that most of us would never use or have even heard of!.
If you are only after the basics and you have a good IP network, then do consider other types of IP phone systems. I've seen Shoretel in use and I'm guite impressed with what it does, considering it is simple to install and manage and the CPU tucks in a rack and the unit I saw could easily be put in a small bag as its very small!.
I personally think that Avaya is quite expensive and the problems we encounter for some sites are very high. Also the support isn't as good as it used to be.
I can't comment on the IP Office system, or Avaya's support but I've seen a couple of them and they aren't that different to the BCM range that they have replaced.
All the best
Firebird Scrambler
Meridian 1 / Succession and BCM / Norstar Programmer in the UK
If it's working, then leave it alone!.