It was the first-ever Palm OS Treo with no external antenna.

The Treo 680 is older, larger, and heavier than the Palm Centro.

An article on the Treonauts weblog includes a good comparison chart and some in-depth commentary.

[2] The Treo 680 was also available from many carriers worldwide including Singtel, Vodafone in NZ & Aus, Globe, Orange France, Swisscom, Telcel MX, Cable & Wireless (Caribbean) and Claro in Brazil.

Initially, Graphite was the only colour available to wireless carriers, with the Arctic, Copper and Crimson models available unlocked exclusively through Palm.com and Palm's retail stores.