I have started using Banckle Live chat support software for my website recently and it not only allows me to stay in contact with my customers all the time but also allows me to combine other collaboration tools also like CRM, Helpdesk, meeting etc which i think is a really helpful feature i will say because i can perform almost all collaboration tasks with this live chat software. You should add this live chat support in your above list also. banckle.com/...
I think it's time to create comparison p3chat.com vs Zopim
This service should be much higher on the list. They provide great info on your customers, and work really well with Adium on the Mac. Top notch customer service as well.
In terms of backoffice support - the best choice available.
Without any doubt the only service that manages to both have advanced features and user friendly interface.
Great app! Nice design, easy and simple to use !