Couple cool things:
- pretty significant performance increase, up to 5x then G1s
- Service Module (SM) replaces Network Module (NM) and the software is decoupled from the hardware. Meaning you can get an SM and install different things like WAAS or Wireless Controller, etc.
- miniusb as a console port (still comes with the regular rj45 console too)
- New IOS packaging - Data, UC, and Security - The IOS tree has shrunk into a bush :) No more Adv this or that... just 3 packages, pretty flat. Each G2 is loaded with a universal IOS image, then an activation lic. (serial and product ID = softward activation lic.) gets installed. New functionality can be switched on with a SAL. Cisco License Manager, Router Call Home, and manual copy and install and the PAK (product act. key) can be purchased through web
- IOS 15 M and T which are follow on to 12.4 Mainline and T.
- ISM replace AIM (and older AIMs for G1s won't be installable on the G2s