If we buy this unit can we install it easily? do we have to pay some license fees to Polycom to activate it??

The Polycom IP 6000 is a Sip enable device which is easily setup by having an automated DHCP scope with options to contact the local http server or TFTP to download firmware and configuration along with a voip registration server. Doing manual settings is possible but more prone to errors. The IP 6000 is an excellent device with clarity and good microphone pickup with options to add additional microphones. They can do three-way-conferencing with options on the display. From my experience the IP6000 has a very poor durability. They seem to last about 3yrs before they stop working or have problems registering with the voip system. Their predecessor the SoundStation conference phones are much more durable and frankly I never seen one go bad. The downside is that they are analog. The only way to do three-way-conferencing is with a conference enabled analog line conducting a flash feature.

What is the quality of voice with this unit? My father is blind and getting hard of hearing. Looking for ultimate clarity and volume.

The sound quality is good. This is an IP polycom that get's hooked up thru the internet - you may want an analog unit that hooks right up to a phone line.that would be a Polycom Soundstation 2.

What warranty comes with this phone?

Polycom doesn't honor the Warranty, They told us the seller is responsible.....At least that's how they are responding to us. Our phone stopped working after 4 months.