This phone was and probably still is the standard by which all other Voice over IP phones are judged. As one of the first players in the VoIP market CISCO
took heft and threw it at creating a very solid platform. While the original CISCO architecture for VoIP was based on a proprietary protocol they have since largely switched to the open SIP
standard. On the materials and construction side of things this phone is a built like a tank. It has serious mass - so much so that it feels a bit clunky sometimes. That said you don't worry about it breaking and it doesn't feel cheap. The buttons have a nice feel to them and the display is big and clear. Sound quality is excellent.
Brendan likes this phone a lot more than Mary does. Mary finds the interface confusing and it requires that you go through a lot of rather obscure menus to do things like turning off the ringer. We used this phone in our bedroom for quite a while, and it is directly responsible for a total ban on phones in our bedroom. The CISCO tended to make random clicking noises in the middle of the night, especially if you accidentally left it in any menu other than the default. The tiny buttons and illegible menus probably would work well in an office setting, but when you are half asleep and just need an ordinary phone, this is not a good choice.