Don't know if you use any, but can CCM support modems? Have them explain how and what is needed.
Do you have to reset the gateway (all trunks) and phones to make changes to say ars routing and set changes?
You always have to reset (crash) something to make any changes. Can your business support it and really work with that?
Can everything (phone system and phones) be managed in CCM GUI? If they say yes their lying. If you want caller ID on an analog trunk, CCM can't support it. Pretty basic, use that as an example and find out what else it doesn't support.
Are they quoting a geotel to do the ACD fucntionality? How are those two peices managed? Do you also have to manage a router for other functionality? What other peices of equipment are needed to make a fully functional ACD environment thats included in a single piece of equipment with Avaya?
What about Micorsoft updates? If Microsoft releases 5 critical ones this week and has to next week due to some virus thing do you have to take CCM down to load them? What can it do that the Avaya can't other than less reliability?
How does voicemail play into what they are quoting? On the voicemail system do you have to rely on third party software stuff from who knows who that's not included in the typical Unity GUI screens?
How about a basic conference call of 6 parties, is it included what's the cost to include it? What if you didn't mention it? If I'm in a conference call of 4 parties how do I drop one of them?
Can a user split thier call forwarding (no answer/busy) and do that from thier phone?
What if you want your personal extenion to forward somewhere but still recieve ACD calls on the same extension?
You really need to have them setup a demo of exactly how you are configured and play with it for comparison for your environment on how your business will use it.