Although not as portable as the C100S I have a
Logitech QuickCall USB Speakerphone which works very well, and I really like this.
However I also have a
Kensington Vo300 USB Internet Speakerphone and it sucks big time as a speakerphone. If you need to connect a microphone & headphones to your laptop via USB then this isn't bad but I suspect there are cheaper options. I've never used the address book feature so I can't comment on that. I paid £8 for it and I think that was far too much. Wouldn't touch it again if you paid me.