From a VAR:
"At the risk of sounding like sour grapes, in my experience no one who has tried to use old Cisco phones and bring them current with their Smartnet coverage so they can use them on a new call manager has saved money. The sad part is they won't know until each phone's current software level is individually checked to find out how much it will be and that won't happen until they are installing the system which is after the point of no return."
"I have heard that Cisco has received a lot of negative press and attention with this strict sequential updating process and has created a one-time "forgiveness" option where [your customer] may be able to update existing phones at substantial discounts. Any "new" purchases of used phones will be subject to the full upgrade process making used phone more expensive than new. Over time a Cisco solution is never the least expensive."
It's tough when you drink the Cisco kool-aid. Like IBM back in the day, no one gets fired for buying Cisco. Until they do. I worked a project with a Private 500 firm that bought AT&T (and VZ as back up), over-spent about $10K per month. He wouldn't buy alternative fiber because they were unknown (to him). Two months later: FIRED!
I see a few firms who have a Hosted VoIP solution - maybe on MGCP, maybe on Skinny - migrating to another Hosted PBX player (on SIP) and they want to keep the phones. It's usually a mess.
As an Agent, I want to be truthful to my clients, so I tell them upfront this isn't going to be pretty or may be a cluster. However, when other agents or another Hosted VoIP provider comes along and says, "That's not true." What can you do? Well, I usually ask, "How much experience do they have migrating customers over? How often do the phones keep working? Can my client speak with one of your customers that did keep their phones?" You have to have the right questions for all scenarios.
Cheaper seldom is.